Server "Hacked" help?

Hey,

Since today someone came to our server called himself a “hacker” last words:
technotronﺠthis server now belongs to #memebloc.add turkslayer on steam for more info

basically what he did was:
technotronsTEAM_0:0:24213184> used the tool stacker on models/props_c17/chair02a.mdl

So i thought as i checked the ranks/files everything would be okay but since he was here clients are dropping (5-8 Clients in some seconds) like every 20-40Minutes which is pretty anoying. Anyone have a idea?

ban him from your server?

He is already banned.

There is an issue with wooden objects breaking in garrys mod, have you tried resetting the server or changing map? If the issues persists, I would check all of your addons and lua folder for any exploits.