Mystical World has beetle entities. It allows to tame them and place them on one's shoulder with Shift+RightClick.
Bettle can be placed back down with Shift+Right-Click on the ground with empty hand.

Expected Behavior

Picking up the tamed beetle.

Actual Behavior

Beetle gets both picked up into player's hands AND get's on player's shoulder.
When placing bettle down, the one on the shoulder stays on and
when Shift-Right-Clicking again dissappears from the shoulder (hense "kinda").

It only happenes with tamed beetles though, since you can't shoulder untamed ones.

Steps to Reproduce

1. Spawn/Locate a beetle;
2. Tame the beetle, using melon seeds;
3. Shift+Right-Click the beetle;

Version of Minecraft, Carry On, Forge

MC 1.12.2
Carryon 1.12.2-1.12.3.15
Forge 14.23.5.2854

Screenshots encouraged

The problem could have been solved by blacklisting a beetle with tamed metadata. But this isn't in the mod, unfortunately.