RTK Surveyin duration

Hello everyone, I am trying here3+ rtk but my surveyin duration vary greatly: Sometimes I get 2m accuracy in10 min, sometimes i dont get it even after an hour. An also I have never observed 2m accuracy in couple of minutes as stated in docs.
I also downloaded Ucenter to debug but I am not sure where too look.
Any suggestions on how to aproach this? what should I compare between runs?