Alright, I'm done trying to find a solution to this. Sure, I use many mods. But I've done my best to organize them and avoid any conflict. I re-installed the game, adding mods one by one and checking if I can load a game. It works for a while, but then rather soon it goes back to this issue. Whenever I load a savegame made in exterior cell, the game would just load infefinitely. I did try alttabbing and switching to task manager (a suggested solution), but with no use. If there's a good soul around seeking to help the helpless and broken, I'd appreciate any assistance.

Here's my load order:


GameMode=Skyrim

Skyrim.esm
Update.esm
Dawnguard.esm
HearthFires.esm
Dragonborn.esm
ClimatesOfTamriel.esm
ApachiiHair.esm
TravellersOfSkyrim.esm
Night Eye Overhaul.esm
SPIKE.esm
Omegared99-Compilation.esm
Ket_ARMONIZER_v2.esm
Skyrim Project Optimization - Full Version.esm
iHUD.esp
SkyUI.esp
ACE BYOG.esp
Dr_Bandolier.esp
ERSO 03 - Super Mighty Dragons Unleveled.esp
ERSO 05 - Dovah Holy Book.esp
ERSO 06 - Wait More Time Dragon Encounter x3.0.esp
ERSO 07 - Mighty Dragon Priests.esp
ERSO 04 - Mighty Odahviing.esp
ERSO 04.2 - Mighty Durnehviir.esp
ToL_Core_by_Brevi.esp
Unofficial Skyrim Patch.esp
Unofficial Hearthfire Patch.esp
Unofficial Dragonborn Patch.esp
Unofficial Dawnguard Patch.esp
StaticMeshImprovementMod.esp
Convenient Horses.esp
Real Wildlife Skyrim 0.1.esp
Ancient Knowledge Armour.esp
AncientDBarmorTSedition.esp
BoundArmors.esp
NoSneakAttackSound.esp
ImpeREAL Empire - Unique Cities - Falkreath.esp
1nivWICCloaks.esp
HitStop.esp
TKRecoil.esp
UFO - Ultimate Follower Overhaul.esp
UFO - Heartfire AddOn.esp
UFO - Dawnguard AddOn.esp
ESFCompanions.esp
Purewaters.esp
PurewatersDG.esp
PurewatersDB.esp
RaceMenu.esp
RaceMenuPlugin.esp
Run For Your Lives.esp
Auto Unequip Ammo.esp
whiteruntrees.esp
Waves.esp
VariedGuards.esp
Unique Uniques.esp
TTS - Ysolda.esp
TravellersOfSkyrim - Vanilla.esp
HT_traveltax.esp
TheChoiceIsYours.esp
TheChoiceIsYours_Dawnguard.esp
Chesko_Step418.esp
Skyrim Flora Overhaul.esp
Skyrim border control.esp
See Your Neighbor.esp
Rainbows.esp
Headtracking.esp
HeavyChitinShield.esp
Oblivion Gates v3 - Skyrim + Dawnguard DLC.esp
Oblivion Gates v3 without Markers - Skyrim + Dawnguard DLC.esp
No NPC Greetings.esp
NEO Brighter Default 200.esp
Night Eye Overhaul.esp
More Dynamic Injuries.esp
LocalizedGuildJobs.esp
Expensive Investments.esp
mjhKhajiitSpeak.esp
mjhKhajiitSpeakDLC - Dawnguard.esp
mjhKhajiitSpeakDLC - Hearthfire.esp
mjhKhajiitSpeakDLC - Dragonborn.esp
mjhKhajiitSpeakMod - NPC Bartering.esp
mjhKhajiitSpeakMod - The Choice Is Yours.esp
mjhKhajiitSpeakMod - Localized Thieves Guild Jobs.esp
mjhKhajiitSpeakMod - Convenient Horses.esp
mjhKhajiitSpeakMod - Realistic Needs And Diseases.esp
mjhKhajiitSpeakMod - Expensive Investments.esp
expensivetraining.esp
BetterQuestObjectives.esp
BetterQuestObjectives-Hearthfire.esp
BetterQuestObjectives-Dawnguard.esp
EnhancedLightsandFX.esp
dD - Enhanced Blood Main.esp
divine_intervention.esp
Detailed Cities.esp
DeadlySpellImpacts.esp
Dead Body Collision.esp
TorchArrow.esp
Dr_BandolierDG.esp
Better Dynamic Snow.esp
Brows.esp
BFSEffects.esp
BandolierForNPCMasterFile.esp
BandolierForNPCsWIC_V2.esp
BandolierForNPCsCheaperBandoliersDawnguard.esp
TorchArrow-Dawnguard.esp
RealisticNeedsandDiseases.esp
RND_Dawnguard-Patch.esp
RND_HearthFires-Patch.esp
RND_Dragonborn-Patch.esp
RND_PureWaters-Patch.esp
RND_USKP-Patch.esp
Chesko_Frostfall.esp
IA6npc01.esp
Lock Requirement.esp
Morning Fogs.esp
Omegared99-WeaponSets.esp
Older Hulda.esp
ReProccer.esp
SkyRe_Combat.esp
SkyRe_EncounterZones.esp
SkyRe_EnemyAI.esp
SkyRe_EnemyScaling.esp
SkyRe_Main.esp
SkyRe_Races.esp
SkyRe_StandingStones.esp
SkyRe_Survivalism.esp
SDO Full-LOD - The Morthal Swamp Light.esp
SDO Full-LOD - Whiterun Trundra Creeks.esp
SkyRe_CraftingFix.esp
ReProccerNONPLAYERfix.esp
DragonbornArmorFix.esp
hothtrooper44_ArmorCompilation.esp
Immersive Weapons.esp
Wandererarmor.esp
Ket_ARMONIZER_LListsNPC.esp
ReProccerDragonborn.esp
FasterArrows100.esp
FasterArrows.esp

I'd suggest you run BOSS. The Unofficial patches alone are out of order and likely not high enough in the load order.