Seems like a character issue. Do you have something written in the rerolling code that might cause him to trigger some kind of SQL injection issues? Do you even use SQL on the backend, I don't know.
Also, is there any way to show what he might have put into his response other than "REROLL" that might've changed the way his character talks to the server to update his position on the map?
This is really strange, I wish I had access so I could help debug it because it'd be fun
