NBT Tag was too big - Kicking players

I've never seen this before. But it just happened recently where I had a couple players started to get booted for this error. I used NBT Explorer and deleted a couple items from their inventories and it seemed to work, but then they get booted again later on. So, can I get some help on what's happening here? Are they glitching items, or do I have a bugged item that's in the server. I'm not really sure what's going on, or what's a good way to prevent this. Thanks!