Unlike vanilla chests, Lootr chests can be opened when there is a full block above it. Some mods (iirc Apotheosis does this) place blocks such as spawners above chests, which should prevent the chest from being opened until the block is destroyed.

I swear I've fixed this, but it's possible that I just haven't pushed it yet. ... Yes, it took me this long to realise.

Yeah, this is fixed.