Hey!
I’m playing on Xbox One, and I initially got the game to play with a group of friends. We jumped right into the co-op campaign immediately and played for a little making some solid progress into the game. As we progressed, naturally I would grab collectibles and weapons that areas had marked (these items are required for 100% completing of some areas). Later into owning the game, I naturally wanted to play single-player to level up quickly, as well as get some extra loot to remain stacked on meds and other items later into the game. The problem is, once I went back into MY story, none of the areas I had completed fully were listed as 100% complete. When returning, the items were missing.
For example, the first time it caught my attention was the area directly above the Saltholmsbro safehouse (AKA Salthomsbro), at which there are two weapons to be collected for 100% completion. These two weapons found in my co-op playthrough were the 44 Magnus and the Automatgevar 5 (both spawns I remember clearly). I collected both in my friends playthrough. However, when I returned to the same location in MY playthrough it told me I had collected neither weapon, but they weren’t spawned in the locations I had found them before. I searched high and low and could not find them anywhere (these were weapons I had in my inventory, as I was on the same character).
Now here’s where it makes me feel it is a bug, I invited my friend into my game who was not a part of the original mix of 4 we had. He immediately found both guns in the locations I had originally, and in doing so HE got me the 100% completion. By finding weapons that were invisible to me.
Naturally, 100% completion is something I would love to go for, but in the current state it seems impossible due to the fact that I am forced to rely on someone else finding the collectibles and weapons based on my memory or their looting skills rather than me being able to simply do it myself. All because I wanted to play the game with my friends on his story-line, and then return to my own later.