Relevant mods:

• Palladium 1.0.9.3
• Sophisticated Storage 0.10.45.912

Items that are placed and displayed in barrels will have their icons be displaced to the bottom left corner, even after reopening the game. the only fix i could find for it was either entirely clearing out the barrel of items, with defeats its purpose, or disabling palladium, which fixed the bug entirely

Weird. Does that happen constantly or only under some circumstances, like having a power?

Happened constantly, with any barrel placed and regardless of the block or item inside. The visual bug in the inventory happens for every player once the barrel enters their entity render distance, and after that the bug persists even after the barrel is no longer in your render distance, even when switching dimensions and the like.