Can you select one with the console and check how long they've been dead for (e.g. GetTimeDead).
Clean Up will disable those actors whose GetTimeDead > iHoursRespawnCell.
Unfortunately, I cannot - they aren't selectable! I almost wonder if the game tried to disable the actors for some reason, was unable to do so (at least graphically), and now I'm watching them get moved out of the active play area and into an unplayable zone (like is done with undeleted and disabled references).
Two other interesting observations: first, some of the dead actors seem to be gone entirely. But it could just be that I'm not able to move to where their bodies are quickly enough to watch them floating away. Second, there's a skeleton from MMM 3.8 I've killed that is standing straight up but NOT moving...
I have provided a link to the savegame that illustrates this problem if anyone wishes to try it - but of course since everyone else will have a different mod order than mine, I can't guarantee that you'll see the same issue - or even that my savegame will load on your machine.
My load order:
Spoiler
Active Mods
? 00 Oblivion.esm
? 01 TR_OoT_Main.esm
? 02 Cybiades.esm [Version 2.0]
? 03 Windfall.esm
? 04 All Natural Base.esm [Version 1.3.2]
? 05 Cobl Main.esm [Version 1.72]
? 06 Mart's Monster Mod.esm [Version 3.8b1]
? 07 Enhanced Daedric Invasion.esm
? 08 TamrielTravellers.esm [Version 1.39c]
? 09 Kvatch Rebuilt.esm
? 0A BathingMod_Base.esm
? 0B TamRes.esp
? 0C Unofficial Oblivion Patch.esp [Version 3.4.1]
? 0D DLCShiveringIsles.esp
? 0E Unofficial Shivering Isles Patch.esp [Version 1.5.0]
? 0F Natural_Habitat_by_Max_Tael.esp
? 10 All Natural.esp [Version 1.33]
? 11 All Natural - SI.esp [Version 1.3.2]
? 12 Immersive Interiors.esp [Version 0.8.1]
? 13 PTAutumnTrees.esp
? 14 Natural_Water_by_Max_Tael.esp
? 15 Idle Dialogue.esp [Version 1.3]
? 16 Atmospheric Oblivion.esp
? 17 Sounds of Cyrodiil.esp [Version 1.1]
? 18 Storms & Sound SI.esp
? 19 All Natural - Real Lights.esp [Version 1.3.2]
? 1A WindowLightingSystem.esp
? 1B AliveWaters.esp
? 1C AliveWaters - Koi Addon.esp
? 1D Better Clocks.esp
? 1E P1DseeYouSleep.esp
? 1F PTFallingStars.esp
? 20 ReneersNotesMod.esp
? 21 Reznod_Mannequin.esp
? ++ shiveringislesdoorusable.esp
? 22 Enhanced Economy.esp [Version 5.4.3]
? 23 Crowded Roads Revisited.esp [Version 1.1]
? 24 Populated Prisons.esp
? 25 C&C - The Blackwood Company.esp
? 26 Enhanced Seasons.esp [Version 1.3.2]
? 27 kuerteeCleanUp.esp
? 28 Map Marker Overhaul.esp [Version 3.9.3]
? 29 Map Marker Overhaul - SI additions.esp [Version 3.9.3]
? 2A DLCHorseArmor.esp
? 2B DLCHorseArmor - Unofficial Patch.esp [Version 1.0.7]
? 2C DLCOrrery.esp
? 2D DLCOrrery - Unofficial Patch.esp [Version 1.0.5]
? 2E DLCVileLair.esp
? 2F DLCVileLair - Unofficial Patch.esp [Version 1.0.7]
? 30 P1DseeYouSleep - DLCVileLair.esp
? 31 DLCMehrunesRazor.esp
? 32 DLCMehrunesRazor - Unofficial Patch.esp [Version 1.0.5]
? 33 Sounds of Cyrodiil - Mehrune's Razor Add-On.esp [Version 1.0]
? 34 DLCSpellTomes.esp
? ++ DLCSpellTomes - Unofficial Patch.esp [Version 1.0.1]
? ++ MaleBodyReplacerV5.esp
? 35 MerryBellInn.esp
? 36 PTArtifacts.esp
? 37 Town_Ceremonial_Armor.esp
? 38 kuerteeHorseCommands.esp
? 39 Weapon Expansion Pack for Oblivion Nthusiasts.esp [Version 1.5]
? 3A DLCThievesDen.esp
? 3B DLCThievesDen - Unofficial Patch.esp [Version 1.0.10]
? 3C Sounds of Cyrodiil - Thieves' Den Add-On.esp [Version 1.0]
? 3D Cobl Glue.esp [Version 1.72]
? 3E Cobl Si.esp [Version 1.63]
? 3F Mart's Monster Mod.esp [Version 3.8b1]
? 40 CurseOfHircine.esp
? 41 CoH 1st Person Anims.esp
? 42 CurseOfHircine - Symphony of Night.esp
? ++ Mart's Monster Mod - RadiantAITweaks.esp
? ++ Mart's Monster Mod - Undead Rise Fix.esp
? ++ MMM-TurnUndeadNPC.esp
? 43 Mart's Monster Mod - Diverse Creatures Expansion.esp [Version 3.8b1]
? ++ Mart's Monster Mod - Diverse Wisp and VASE Addon.esp [Version 3.8b1]
? 44 MMM Mummy.esp
? ++ Mart's Monster Mod - Diverse Imperial Armor.esp [Version 3.8b1]
? 45 Mart's Monster Mod - Gems & Gem Dust.esp [Version 3.7b7]
? 46 Mart's Monster Mod - Hunting & Crafting.esp [Version 3.8b1]
? ++ Mart's Monster Mod - Looting NPCs & Creatures.esp [Version 3.8b1]
? 47 Mart's Monster Mod - Zombies for Body Meshes.esp [Version 3.8b1]
? ++ Mart's Monster Mod - Less Reavers.esp [Version 3.8b1]
? 48 Mart's Monster Mod - No Carrion Rats.esp [Version 3.8b1]
? ++ Mart's Monster Mod - Spawn Rates - Reduced Reduced.esp [Version 3.8b1]
? 49 Mart's Monster Mod - City Defences.esp [Version 3.8b1]
? 4A Mart's Monster Mod - Curse of Hircine.esp [Version 3.8b1]
? 4B Mart's Monster Mod - Farm Animals.esp [Version 3.8b1]
? 4C Mart's Monster Mod - Diverse WaterLife.esp [Version 3.8b1]
? ++ Mart's Monster Mod - Slof Horses Complete.esp [Version 3.8b1]
? ++ Mart's Monster Mod - DLCHorseArmor+Slofs .esp [Version 3.7b7]
? ++ Mart's Monster Mod - Diverse Runeskulls Loot G&GD.esp [Version 3.8b1]
? 4D TamrielTravellers4MMM.esp [Version 1.39c]
? 4E TamrielTravellersItemsCobl.esp [Version 1.39c]
? ++ TamrielTravellersItemsVendor.esp [Version 1.39c]
? ++ ShiveringIsleTravellersFriendlyFactions4MMM.esp [Version 1.39c]
? 4F kuerteeWanderingEncounters.esp
? ++ MMM-Cobl.esp [Version 1.69]
? 50 Trade and Commerce.esp
? 51 AdenseEpicDungeon.esp
? 52 Ancient_Goblin_City.esp [Version 2.5]
? 53 BHC_Expanded.esp [Version 1.2]
? 54 Blackrock_Mountain.esp [Version 2.7]
? ++ Dancer_Undress0_6.esp
? 55 Deathtrap Dungeon.esp
? 56 Jagnot- Imperial City Library V1.3.esp
? 57 Kragenir's Death Quest.esp [Version 2.11]
? 58 KDQ - Rural Line Additions.esp
? 59 Kvatch Rebuilt.esp
? ++ Kvatch Rebuilt Weather Patch.esp
? 5A Lair_of_the_Hydra.esp [Version 2.5]
? 5B LetThePeopleDrink.esp [Version 2.5]
? 5C KragenirsDeathQuest-LetThePeopleDrink patch.esp
? 5D LostSwordOfTheAylied.esp
? ++ LostSwordOfTheAylied - OBSE Add-On.esp
? 5E PinePeakLodge.esp
? 5F SingingStablehandInn.esp
? 60 SleepyCatInn.esp
? 61 TheWellOfMinlorada.esp
? 62 The Ayleid Steps.esp [Version 3.4]
? 63 The_Dragon_Citadel.esp [Version 1.5]
? 64 The_Tower_of_the_Lich_King.esp [Version 2.5]
? 65 TR_Stirk.esp
? 66 Stirk_Compatibility_Patch.esp
? 67 VHBloodlines 1.2.esp [Version 1.5.6]
? 68 Windfall.esp
? 69 Cyrodiil Travel Services.esp [Version 3.0.5]
? 6A Arena Lite.esp
? 6B DLCBattlehornCastle.esp
? 6C DLCBattlehornCastle - Unofficial Patch.esp [Version 1.0.6]
? 6D DLCFrostcrag.esp
? 6E Kvatch Rebuilt_Frostcrag.esp
? 6F DLCFrostcrag - Unofficial Patch.esp [Version 1.0.6]
? 70 BrumaGuildReconstructed.esp [Version 1.0.1]
? 71 Knights.esp
? 72 Knights - Unofficial Patch.esp [Version 1.1.2]
? 73 SM Plugin Refurbish(Merged).esp [Version 1.30]
? ++ Mart's Monster Mod - Knights.esp [Version 3.8b1]
? 74 Sounds of Cyrodiil - KOTN Add-on.esp [Version 1.0]
? 75 Cybiades.esp [Version 2.1]
? 76 CybiadesDungeon.esp [Version 2.1]
? 77 RTT.esp
? 78 RTT-Weye Relocation Patch.esp [Version 2.0.1]
? 79 Lost Paladins of the Divines.esp
? 7A AFK_Weye.esp [Version 2.32.COBL]
? 7B MannimarcoRevisited.esp
? 7C Enhanced Daedric Invasion.esp
? 7D ReclaimSancreTor.esp [Version 1.0.4]
? 7E road+bridges.esp [Version 4.6.3]
? 7F Faregyl.esp [Version 2.0.8]
? 80 Feldscar.esp [Version 1.0.13]
? 81 Molapi.esp [Version 1.0.1]
? 82 Reedstand.esp [Version 1.0.3]
? 83 Urasek.esp [Version 1.0.2]
? 84 Vergayun.esp [Version 1.0.9]
? 85 NakedNord.esp
? ++ NRB4+LtPD Patch.esp [Version 3.0]
? 86 Bartholm.esp
? 87 bartholm - EE patch.esp [Version 4.2]
? 88 Frostcrag Village.esp [Version 1.0.7]
? 89 Salmo the Baker, Cobl.esp [Version 3.09]
? 8A Sutch Village.esp [Version 1.0.2]
? ++ Natural_Vegetation_by_Max_Tael.esp
? 8B Harvest [Flora].esp [Version 3.0.0]
? ++ Harvest [Flora] - DLCVileLair.esp [Version 3.0.0]
? ++ Harvest [Flora] - DLCFrostcrag.esp [Version 3.0.0]
? ++ Visually Realistic Lava.esp
? 8C AutoBookPlacer.esp [Version 3.02]
? 8D Auto Update Leveled Items And Spells.esp [Version 1.2.5]
? 8E BFG's Open All the Gates.esp
? 8F Cliff_BetterLetters.esp [Version 1.2]
? 90 Dungeon Actors Have Torches 1.6 DT.esp
? 91 PersuasionOverhaul.esp [Version 1.43]
? ++ PersuasionOverhaul_MMM.esp [Version 1.2]
? 92 Ring of console.esp
? ++ Enhanced Economy - House prices.esp [Version 5.4.3]
? 93 BathingMod_Soap.esp
? 94 BathingMod_Bathroom_Upgrades.esp
? 95 BathingMod_Placeable_Bathtubs.esp
? 96 BathingMod_InnsHaveTubs.esp
? 97 RealisticFatigue.esp
? 98 RealisticHealth.esp
? 99 Basic Primary Needs.esp [Version 5.5]
? 9A ReneerKeyLockMod.esp
? 9B AgarMoreVariedSpellEffects.esp
? 9C EnchantmentRestore.esp
? 9D RenGuardOverhaul.esp
? 9E kuerteeClothingMatters.esp
? ++ Marksman Velocity SI.esp
? 9F kuerteeAttributeAndSkillBasedDamageModifiers.esp
? A0 Duke Patricks - Near Miss Magic And Arrows Alert The Target.esp [Version 7.1]
? A1 Duke Patricks - Fresh Kills Now Alert The NPCs.esp [Version 4]
? A2 Phitt's Phighting Phixes.esp
? A3 BFG's Enhanced Armory.esp
? A4 bgBalancingEVCore.esp [Version 10.52EV-D]
? ++ Mart's Monster Mod - Resized Races.esp [Version 3.8b1]
? A5 bgMagicEV.esp [Version 1.7EV]
? ++ bgMagicSpellTomes_for_WryeBash.esp [Version 1.68EV]
? ++ bgMagicItemSigil.esp [Version 1.68EV]
? ++ bgMagicEVStartspells.esp [Version 1.68EV]
? A6 bgMagicBonus.esp [Version 1.7EV]
? ++ bgMagicEVAddEnVar.esp [Version 1.68EV]
? A7 bgMagicEVPaperChase.esp [Version 1.68EV]
? ++ bgMagicAlchemy.esp [Version 1.57]
? ++ bgMagicPotionNumberSoulGemValue.esp [Version 1.68UV]
? ++ bgBalancingEVOptionalClasses.esp [Version 9.0EV-U]
? A8 bgBalancingEVLAMEAddition.esp [Version 10.51EV-D]
? ++ bgBalancingEVLAMEGlue.esp [Version 10.0EV-D1.62EV]
? A9 bgIntegrationEV.esp [Version 1.0b]
? AA kuerteeDetectLifeEffectNightEyeShader.esp
? AB BubbleFx.esp
? ++ NRB4 Standard Road Record.esp
? ++ CoreRandmonClothing4Npcs.esp
? ++ Storms & Sound - Filter Patch.esp
Affected savegame and associated OBSE cosave:
http://www.filedropper.com/memorialcaveflyingbodiesglitch