Im in Initiation 5 right now, and just got the key to room 101. One of the chests in the room had 2 boxes of flare gun ammo, but I didnt have enough inventory space to grab them both. So I went to the safe room right next to it, dropped a stack in the shoebox, then went back over, grabbed some more, but both boxes of ammo were still there. I repeated this multiple times and the boxes never disappeared. After making more room in my inventory, I went back and tried to grab all of it and ended it up with 2 stacks + 1. Reloaded the save to see if that was the limit but no, still there.

So what I think what is happening is that entering a safe room while a stack of items is still on the ground nearby causes the stack to refill itself. I dont know if this only applies to stuff in a chest or if stuff on the ground dropped by Taken for Saga would also work.

EDIT: Video