Tacx flow

Hi guys , I have a flow and from my first with calibration it seem to run good , 2nd week stop working . Tacx support said clean the turbo brake and loosen it a bit , did that and it worked , 3rd week same problem same solution. Also had to recalibrate every time . Q1 - how tight should the wheel be on the turbo, just touching or a big dip in the tyre!! Q2 - should I have recalibrate every time I go on zwift or when I have a problem with it ? TIA