I have the same issue too, it happens during parrying attacks. Not just weapons, but apparell disapper during melee.

Each successful parry consumes weapon durability, because well... colonist use them to block attack. Same for armor. They aren't "disappearing" they're destroyed.

引用自 I.C.E.：

Each successful parry consumes weapon durability, because well... colonist use them to block attack. Same for armor. They aren't "disappearing" they're destroyed.

No, they are really not.

The Durability does decrease if you are engaging in melee as you said, but the bug here is not that at all. The rifles in question disappeared shortly after the colonists started shooting, they disappeared BEFORE any of the colonists had engaged in melee combat!

This has been quite a gamebreaker bug, I even uninstalled the mod a few games after that because the bug kept happening on several occasions, really can't tell what triggers it, but it does happen at least once every game.