TL;DR this is correct behavior. Some part of gun is at 70%, overall status jumps to that on pickup.

Yuki(dev): ".. the condition is only updated by this mod when you pick it up for the first time. So it looks really misleading sometimes, sorry for that but it was a compromise because I was just trying to get to release.

The mod should be compatible with pretty much any other gun mod, but you won't be able to disassemble custom guns without support."

Yuki(dev): "Right now, any guns you loot will always have fully working parts with conditions between 70% and 100%. This was done intentionally for testing and balance purposes in the initial release. I do want to add a sandbox option to allow changing the likelihood of finding working parts in looted guns."

Drizzt: "..and the gun's overall condition will always show the condition of the worst part - and so even though a gun may show 70%, you may only have one 70% component and the rest may well be higher."