This is a bug with Unreal’s net driver (the system that handles networking in Unreal). We made a custom fix back in October, which resolved it. However, we had to revert this fix as it was causing players to disconnect from servers randomly. From what I’ve been told, it’s a very complex issue that happens when an item changes network ownership and it causes it to wrongly delete the item from the client. It’s very rare that it happens.
However what you are describing seems a lot more common, which I have not personally experienced on my end and I play Tower with friends every day. I’d suggest verifying your game cache, check your networking connection with the hosts you are playing with. Try to note when this happens and what the cause is.
One solution for us is to upgrade the engine version and hope the bug was resolved. Upgrading the engine would take several months and introduce countless other bugs, which would not be feasible before 1.0. Going 1.0 does not mean we are done with the game.