Because Mimicubes copy the user's item/armor with full durability, if the player has access to a "disarm" effect from another mod that makes mobs drop held/equipped items (such as the Breaking Aim perk from Astral Sorcery or the Disarm enchant from Cyclic), then it can be used to easily get a full durability copy of your equipment.

While this might not be a big deal in some modpacks, since Mimicream can dupe equipment anyway, the free full repair can easily result in some broken interactions in other packs.

I believe an easy fix to this would be to make Mimicubes copy weapons/armor with only 0 durability, so even if you disarm them, you don't get a free full repair on your items.

yeah, that's a good idea for a work around.