Plus, I don't know what I can toggle in the config to alleviate this

Try disabling releaseSpriteFramesCache.

The molten metal is supposed to be flowing down, not being static

Using LoliASM v4.4

For the record, I believe disabling textureFixes from VanillaFix will reduce the FPS substantially on AMD GPUs due to the fact that reuploading the textures each frame is extremely slow on them, unless releaseSpriteFramesCache does the same thing. Even on my Nvidia card I have found this VanillaFix optimization to actually be quite effective; when profiling the slowness in 1.16 I noticed that uploading animated textures took up a substantial part of the frame time. The VanillaFix beta for 1.16 made that issue go away.

Yeah, I think I see exactly why VF's textureFixes makes this happen. I'll jot this down for when I'm working on the fork. It's also possible that I'd just work up something similar or better in https://github.com/CleanroomMC/Blackbox/

Oh? Good news. I always thought LoliASM had something to do with it...

Even when releaseSpriteFramesCache is false?

Can confirm this is happening also with version 4.8.

@Rongmario Sorry for the misunderstanding - I did not test it beyond the default configuration, I will try to with your suggestion soon.

That's no problem.

@Rongmario I can confirm this is still an issue with releaseSpriteFramesCache disabled.

What about disabling squashBakedQuads?

@Rongmario Still an issue with squashBakedQuads disabled.

@Rongmario Wait, I think more testing is necessary - I just completely removed LoliASM and this is still an issue 👀

Quite marvellous. I hate Tinkers' Construct.

Do you have textureFixes enabled for VF? Provided you're not using the dynamic model loading version of VF.

Do you have VanillaFix installed?

I do - and I can see where this is going

@Rongmario No worries, this is not your or your mod's responsibility, but thank you for the will to help make modded Minecraft better! If you do rework VanillaFix I'd be sure to include it in my modpacks, and I am currently testing LoliASM.
About this issue, you can probably close it as it is a VanillaFix issue.

I do have textureFixes enabled, and I can see that this issue with VanillaFix and Tinkers animated textures was reported in the past but I guess was never fully resolved - DimensionalDevelopment/VanillaFix#39 (comment)

Yeah, I'm going to fix this soon, got way too many projects going on atm. Even a VanillaFix fork/rework is on the table.

Thank you, but I think I'll keep it open for the time being as I think releaseSpriteFramesCache may have the same effect as VF's textureFixes. However, they don't quite do the same thing.

Also, I'm joined with quite a few others on trying to make 1.12.2 modded better w/ more support, we are quite ambitious: https://cleanroommc.com/

I tested Tinkers' Construct with LoliASM (with releaseSpriteFramesCache enabled), without VanillaFix, and this issue is not present - the textures animate properly.
And, that's awesome - I joined your Discord server!