Do not you think that the images should be optimized? Resources size in assets\chisel\textures is scary - more than 50 megabytes.
OptiPNG -o7 decreasing size to 2,03 MB. No textures glithces in the game was observed. But are possible with transparent blocks\items.

Thanks for the tip, I had done this a while ago, but not since we retextured quite a bit of the mod. Photoshop's default export is garbage and results in bloated files apparently :)

I didn't even export as png, I did save as png. There's actually a difference 😅

Is there any change to the jar?

Chisel-MC1.12-0.1.1.28.jar - 17 345 667
Chisel-MC1.12-0.1.1.28 (optiPNG).jar - 4 278 811