Shadow billboard-like effect bug appearing randomly on interior cells

• What is your operating system? Windows 10 Pro with an AMD Ryzen 5 5600 and RX 6700 XT (newest drivers installed).
• What version of OpenMW are you using? If you used a bleeding edge build, state the exact revision used. RC7.
• What version of Morrowind are you using (i.e. retail CD or Steam)? What addons (Tribunal, Bloodmoon) do you have installed? What language is your Morrowind install? Steam Version with all the addons enabled.
• Do you use any mods? If so, does the problem also occur in a clean vanilla install without any mods? I tested this on a very lightly modded build. Only mods i installed are a few animation replacers and some lighting mods like ImprovedLightsforAllShaders. I also installed S3ctor's LightFixes. The issue persists with or without post processing enabled.
• What are the exact steps to reproduce the problem? This issue happens on interiors only so far from my testings. I encountered this on 0.48 and old 0.49 dev builds as well. When i migrated on 0.49 RC builds i didn't encounter any shadow related bugs (like terrain shadows appearing out of nowhere), until now. This bug appears at random but in most cases after i reload to a different save, inside a interior cell.
• What did you expect to happen? What happened instead? I haven't enabled interior shadows but this billboard-like effect shouldn't happen (on 0.48 or old 0.49 dev builds, enabling interior shadows sort of fixed it iirc).
• Are there any error messages in your openmw.log file? If you're not an OpenMW team member, it's best to upload it. None. But i will upload the log, the settings file and a video if you find something from there.

clip_1_747_589_171_083 settings.cfg openmw.log

Edit by AnyOldName3: Missing line break.