I tried to overwrite general_icons.png in my resource pack with this general_icons.png

However, shulker box buttons are rendered incorrectly: screenshot (arrows are behind boxes)

Any idea why this could happen or how I could avoid it?

Note that there are multiple shulker boxes in the sheet. Just make cut outs for where the arrows will be.

Don't ask me why I made it like this. It just ended up like it somehow.