I've been attempting to play through The Ultimate Heist quest for the Thieves Guild, which has gone smoothly until entering the cell "The Lost Catacombs". The cell successfully loads, but as soon as I try to move further in, the game crashes without any kind of warning. Would this be caused by a mod issue?

Here's my load order:

Oblivion.esmAll Natural Base.esmFrancesco's Leveled Creatures-Items Mod.esmFrancesco's Optional New Items Add-On.esmFrancesco's Optional New Creatures Add-On.esmTamrielTravellers.esmOpen Cities Resources.esmUnofficial Oblivion Patch.espTNR ALL RACES FINAL.espTNR - ShiveringIsles.espYounger Hotter NPC's v1.0.espUOP Vampire Aging & Face Fix.espOblivion Citadel Door Fix.espDLCShiveringIsles.espUnofficial Shivering Isles Patch.espAll Natural - Real Lights.espAll Natural.espAll Natural - SI.espEnhanced Water v2.0 HD.espWindowLightingSystem.espAliveWaters.espAliveWaters - Koi Addon.espAliveWaters - Slaughterfish Addon.espAFK_PrayerIdles.espP1DrobesOver.espP1DlookHereYou.espCrowded Cities_Open.espCrowded Roads Revisited.espEVE_StockEquipmentReplacer.espextavegant masks.espSlof's Horses Base.espFrancesco's Optional Files.espTamrielTravellers.espShiveringIsleTravellers.espFransfemale.espExtended Imperial City Version 1.0.espExtended Chorrol Open Cities.espExtended Skingrad Open Cities Complete.espBrumaMGRestored.espKnights.espEVE_KnightsoftheNine.espxulStendarrValley.espXulEntiusGorge.espxulFallenleafEverglade.espxulColovianHighlands_EV.espxulChorrolHinterland.espxulBeachesOfCyrodiilLostCoast.espxulBravilBarrowfields.espxulLushWoodlands.espxulAncientYews.espxulAncientRedwoods.espxulCloudtopMountains.espxulArriusCreek.espxulPatch_AY_AC.espxulRollingHills_EV.espxulPantherRiver.espxulRiverEthe.espxulBrenaRiverRavine.espxulImperialIsle.espxulBlackwoodForest.espxulCheydinhalFalls.espxulAspenWood.espxulSkingradOutskirts.espxulSnowdale.espOpen Cities Outer Districts.espOpen Cities Reborn - Full Merge.espOCC-ULCH-Patch.espOCLR+ULBWForest Patch.espOC+Cheydinhal Falls Patch.espOC+ULSkingradOutskirts Patch.espHarvest [Flora].espEVE_ShiveringIslesEasterEggs.espDungeon Actors Have Torches 1.6 DT.espExterior Actors Have Torches 1.3 DT.espEnhanced Vegetation [125%].espRealisticForceMedium.espRealisticMagicForceMedium.espMighty Magick - Settings.espMighty Magick - Spells and Creatures.espMighty Magick - Shivering Isles.espMighty Magick - Races.espBetter Redguard v2.espFrancesco's 10 days respawn time - 1-20 day lenght rescale.espP1DshieldNoGlow.espomg-staticDoF.espOpen Cities Reborn Road Record.espBashed Patch, 0.espMK_Mask.espThe Undead Arise 2.0.esp

Thanks a million for any help you can give.

Does anybody have any ideas? I really have no idea how to give any more information.

No idea, really, but as the Lost Catacombs has lots of Undead it could be a bad spawn from Fran's Optional New Creatures Add-On perhaps. Never used it so no idea if it has such issues. Anyway, if so you could try loading from a save before entering the catacombs and wait 11 days (as you're using 10 days respawn) for a respawn before entering. Never used The Undead Arise 2.0.esp either, but as it concerns undead you could also try loading the save without it. Noticed one post on TES Nexus that mentioned issues with the Unofficial Patch but no idea if that's correct or not. Might be worth a shot.

Thanks for the tip, though I eventually was able to get through without actually doing anything.

My game tends to hit spots every once in a while where it just gets very temperamental and crashes repeatedly. Is there any tool or mod that decreases overall crash rates in general? I'm now stuck in Echo Cave with the same problem as before.