I don't know if this is intended enemy behavior, but during a adventuring fight with 1 spider and a supply crate, the spider was able to reach the supply crate and refused to move off it, even after it set up hide, it wouldn't go into melee to use backstab against any of my cats, who were chilling out of range enough that if the spider went to attack it'd move off the supply crate.

Like, I sat there for several turns to see whether the enemy would move or not and it did not. Maybe because my cats were spread out nearby it decided to just wait instead of attack?

I didn't manage to get a screen shot of it sadly before moving on just being annoyed the enemy was denying me my 2exp for my cats. Oops.

Wow that was rude of it! The monsters don't know about the crates at all, and I thought it wouldn't be a problem because you can stand on defeated enemies.... forgot about what might happen if the last monster / only monster is standing on it and doesn't want to move.

Spiders particularly have different AI because of the hide skill, they're pretty much always going to sit there and hide unless you're in range, so it's possible other monsters won't be as inclined to camp the crate. (Their AI essentially says "if hiding, backstab. if not hiding, hide. if backstab out of range, hide").

One possible way to get it to move would be to stand adjacent to it. Monsters are coded to circle around cats when using melee attacks, so there's a very good chance (75%) it would have moved from the chest to another adjacent space and you'd then be able to grab the item. Hiding behind trees or re-positioning may have worked for other kinds of monsters, but probably not for the spider because of its love for hiding.

There's no RNG involved in where monsters choose to go when using skills that aren't melee attacks. They exclusively triangulate the tile with the greatest distance from all cats, so if the cats don't move, they won't either. A spider vs spider battle would most certainly stalemate as they stare at each other from across the map forever.

Also had this issue with a spider, he's currently sitting on my box :(

Update: having my cat stand next to him and take a hit did work, however, this was not a great long-term solution since it meant my cats have to take damage/give an enemy a free hit in order to my box.

this just happened to me you can see the outline of the chest, i spent a whole turn to get to the crate only for the enemy to stand on top of it