[tor-relays] Refuse Guard flag

Hello there. I have been running my (non-exit) relay without issues for some months. Recently I noticed that my ISP started to reset my IP a few hours after the node gets the Guard flag, thus making it lose such a flag (as well as Stable and HSDir). I am not sure if the Guard flag is the real cause, but it is the only condition that is verified always and only right before I get a new IP. Is there a way I can keep my node running with the same settings but preventing it from becoming a guard, to investigate if the flag is the real cause? Thanks,

Eldalië