When you lose HRV, does the mode change to 8, test request? If it does you are getting a fault and it’s taking itself out of service. Look at Display 1 and look at the bottom 2 rows. If any of those are high, look into that fault. May be missing the vane, getting lost, or you might have a flakey up slowdown switch so it sees top and bottom open at the same time when the bottom opens.