Pots not splashing

So I'll get straight to the point. I've created this duel plugin and people can go into queue and fight.. etc. When people join a queue and get matched up, they can throw their first row of pots (their hotbar) and it works just fine, but when they try to put more pots or anything actually into their empty hotbar spaces it doesn't work. You can visually see that the item is going into their hotbar but it doesn't register on the server. When they try to splash pots it just gets removed from their inventory, or when they try to drop the item it does the same thing. Any idea as to why it could be happening. Is there a event that I could be canceling or anything of that nature. I'm not looking for code but more as in why or how it could be happening.

https://gyazo.com/371e63cd278e43e3adbae528d020756d heres a gif of what is happening

If you don't understand please tag me and I'll try to explain better.

 

Post the code.

 

Are canceling the player interact event? Are you hiding players using packets and accidentally hid the own players packets? Have you tried healing yourself even though you cant see the animation?