Network Protocol Error

for some reason whenever me (LogyBanana) or (Exp_YT) joins the server and gets anything done team wise, it kicks everyone on the server. Now originally we thought it might of been an issue with Pufferfish 1.21.3 but we switched to paper and the same thing happened.
Can anyone help? (or has anyone had the same issue?)

I'll also add, nothing appears in console except for leave messages.