CycleOps Magnus Clutch Issue/HR question


I have been using this wheel-on trainer for about three years now.

Before tonight’s ride I pumped up the tire to 110psi, tightened the clutch knob until it clicked, ran the calibration in the Rouvy app, then did a 75-minute threshold (Starr King) workout.

The resistance during the workout felt maybe a little bit lower than expected - though the 3x15 minute intervals were mentally and physically challenging to complete. Pushing boundaries here at the end of a 3-week threshold block. Further, my HR was a good 10-15bpm lower than I would expect to see for this RPE (maybe a 9/10). After completing the workout I decided to check the clutch knob and I was able to turn it quite a bit before it clicked again. I interpreted this to mean that perhaps the power readings during this workout were inaccurate.

Is this normal (perhaps a side-effect of the calibration) or is it an indication that the clutch is not holding correct pressure on the tire throughout the workout? And if it’s the latter, is there anything to be done about it? Is the low HR for a high RPE an indication of fatigue?

Trying to reconcile the high RPE with the low HR and the strange clutch issue. Very confusing.

Appreciate any input!