Most with GSOs prefer to pull the mirror down a fair way so the springs are well compressed. Some have found the springs to be weak, so if they are not compressed the primary mirror may "flop" about a bit - so you lose collimation as you adjust scope altitude.
Suggest that you collimate at about the altitude where you want to observe. If it is everywhere (
) then collimate at around 45 deg. Then move the tube unit vertical and check collimation, then move it horizontal and check collimation. The is easily done with a laser collimator since you can watch the return dot through the laser window as you move the OTA. If you are getting a fair amount of movement in collimation, pull the primary down further (springs more compressed) and try again.