Hello there. As the title says, source jars be a bit odd. Nothing game breaking though. I'm using "ars_nouveau-1.16.5-1.24.21" and "geckolib-forge-1.16.5-3.0.65", Patchouli as well but I doubt that's affecting this small issue. Potion Jar and Potion Melder do not have this issue. I still get info in the upper left corner about how full it is so no problems there. Here's two pictures:

Yep, using magnesium. Can I mess with some settings in magnesium to fix this? If not and I have to remove magnesium to fix this, then I'll just ignore the odd rendering. Magnesium has been an actual boon for me for higher and smoother fps, unlike Optifine.

This is common with mods that change rendering. Optifine, magnesium, etc. Are you using any of those?

I am not sure of any setting within Magnesium, but it has been a common issue.