I believe you have a conflicting admin mod or addon.
ULib and ULX perform no IP ban function, and your console indicates "Writing banned_ip.cfg".
We don't ban by IP, we ban by steam ID, as that is more challenging to slip by/get around. (Not impossible, just more challenging).
If you were to see any message by ULX, it would be "Writing banned_user.cfg", not _ip.
The error appears because your conflicting addon or admin mod has removed the player entity before ULib can finish gathering information about it and then also removing it.