Just make sure every slot is filled. I realized this a bit too late, but nonetheless it works til Bungie does something about it. 4 slots for glimmer consumables, 4 slots for items you turn in for 200 glimmer, 1 slot for keys, a few for heavy, 1 for primary synth, and then a few left for special. Just don't turn in the Cabal Codes, House Banners, etc. If you need the money, use the app or website to move 1 to your vault, turn in the rest, then pick that 1 back up to take up space.