Tested on 1.19.2 fabric.

Supplementaries mod jars can contain any liquids. So by default if milk bucket used on jar - jar data nbt become:
supplementaries:jar {BlockEntityTag:{FluidHolder:{Count:4,Fluid:"moonlight:milk"},Items:[]}}
-- this modified a little because of moonlight lib usage in my modpack

But with your mod installed jar nbt data turn into:
supplementaries:jar {BlockEntityTag:{FluidHolder:{Count:8,Fluid:"travelersbackpack:milk_still"},Items:[]}}

This data makes a lot of things imposible to do... For example fill bottles with milk (Farmers Delight mod feature)

This thing is really annoing, so please fix it. (You can switch to moonlight:milk [easiest solution in my opinion])...

Found actual source of bug. Closing issue.