Like the title says, I'm unable to add anything to a barrel unless it's first in the shield slot, after that I can add from inventory like normal.

In testing, I've been able to add and extract from barrels properly-- it seems like I'm missing something. Could you perhaps come up with a few specific steps to reproduce this issue? Additionally, if any other mods are present, could you provide a list?

Ok, I just loaded up my game, and I'm able to place items as normal. So possibly just a temp glitch. Everything is working the way it's supposed to now.

In that case I'll close it for now, glad it works! If something similar happens again feel free to return to this issue.