Strange visual bug

[JaiGanesha]

What could this be? This happens to me once out of a twenty times only in Fort Satch. If you save the game at this point and load it again, the models are displayed normally. After restarting the game, the bug does not repeat at all, no matter how much I tested. The bug can only occur after restarting the PC and launching the game for the first time.

https://ibb.co/xqJ2t2t3

https://ibb.co/TDvNVkWp

Edited July 2 by JaiGanesha

[RomanR]

It looks like typical model or animation vs. skeleton problem (streched vectors because of missing referenced bones in skeleton's model). As I see this glitch only on women, I guess you're using something made for Better Bouncing Breasts (BBB in short) mod, but something is missing.

[JaiGanesha]

I don't use anything like that. I have absolutely no mods to improve models or new clothes. Vanilla. And this bug occurs very strangely, only in Fort Satch. It doesn't appear anywhere else.

I disabled absolutely everything except unofficial patches, engine bug fix and display tweaks and... this bug still reproduces.

Edited Wednesday at 09:11 PM by JaiGanesha

[RomanR]

Unofficial patches? For example Oblivion Unofficial Patch adds its own models for armor or clothes which are supposed to fix something, so you can't be sure (although there are only handful of models for females in this mod). And it also means that these models are used regardless of activated esp or not, if they were made to be replacements. So if you find Clothes or Armor directories in Data/Meshes/, it means that you installed some mods which added them. Same for skeleton models - if you see Skeleton.nif or SkeletonBeast.nif file in Data/Meshes/Characters/_male/ directory or Skeleton.nif in Data/Meshes/Characters/_1stperson/ dir, they're added by mod. Vanilla doesn't need loose files, as they're already in their bsa archives.

Still, seeing this glitch only for a first time and only in one place makes it hard to diagnose. First step would be to try without OBSE (Oblivion doesn't need it on its own, so it should be the safest try) and then try to unistall mods one-by-one or even go completely vanilla to find what part could be responsible (OBSE or its plugins or mods).

Edited Thursday at 09:09 AM by RomanR
1stperson -> _1stperson

[JaiGanesha]

I disabled all mods and even OBSE and after loading the game I saw this bug. Then I made a new installation of the game and installed unofficial patches, then started a new game - the bug is gone. But after loading an old save the bug appeared again. It follows that the bug's information is written to the save. Now I have a difficult test - I add ten mods every time and start a new game until the bug appears again. 
I have already tested the only two animation mods in my collection - NIARA and new eating animations and these are not them. Sooner or later I will identify the culprit and report. As modding practice has shown - this may even be the most unexpected mod.

Edited Thursday at 09:52 AM by JaiGanesha

[JaiGanesha]

I tested all mods from the build except Ultimate Leveling when starting a new game and the bug was not reproduced. I will test UL in several scenarios to repeat the bug. There is also a suspicion on Enhanced Mounting Combat, since that time there was an animation glitch when the character was riding a horse. It is possible that this is somehow related, but it is not a fact, since I have already encountered this bug during early testing.

Some scenario or coincidence causes this. It may be that this is an engine bug.

Edited Friday at 12:26 PM by JaiGanesha

[JaiGanesha]

 

I found the mod that is causing this bug!

 

https://www.nexusmods.com/oblivion/mods/50205?tab=description

 

Somehow the backpack slot stretches the NPC's shoulders or arms and the bug only appears in Fort Satch. The bug occurs if you put on a backpack or backpack with a cloak and enter Fort Satch. It can happen immediately or after several save loads. I tested several scenarios several times and am now 100% sure.