Before Continuing:

• Check you are using the latest version of the mods and its dependencies
• Always include a latest.log if you are crashing
• Remove mod that enhances Minecraft: Optifine, Sodium, others. The issue persists.
• If you are unsure which mod is the culprit.
  Disable all of your mods and enable them 1-2 mods each time to isolate the culprit
• Confirm that there is no existing issue with a similar description submitted in the list of issues.

Version

1.20.1-FORGE

Supplementaries Version

1.20 3.1.12

Moonlight Lib Version

1.20 2.13.58

Describe Issue

To be honest, this falls right in between a feature and a bug report, and I cannot tell which is it. For the maintainer reading this, feel free to change it.

It is normally not possible to fill a jar with fluid when it contains a mob. However, doing so with commands works. And it aesthetically looks just fine. However, right-clicking with fluid containers doesn't work, nor does extracting fluid with the Faucet.

To be clear, the problem is not that you should be able to fill the jar with both at the same time normally, it's that interacting with the liquid is entirely impossible when the mob is inside.

you are telling me I can't put my fish into jar full of water? what a shame...

yeah its not meant tocontain both. its giving priority to the mob interaction

As a bit of further context, a friend got confused and thought it was possible to crush a cow into a Jar, but got confused with the iconic Cooking for Blockheads. So, I decided that it should be possible, as a joke. Lychee Tweaker made this easier, but it required a bit of meddling with commands.

Every random tick it should fill itself with milk to be obtained. Problem is -- ah well -- it doesn't really matter. It's not functioning as intended for the issue reported above.