Fix is not constant and changes base-line with static bases

Hi welcome.
At your location there are multiple 2-3 story building right next to your rover and base.
You should move away from tall buildings and obstruction that will block your skyview at low angle and possible multipath.
Working that close to a building might challenge the accuracy, base/rover should not be that close to a wall.
I am confidente that you will get a satisfying result in a more open area.