I completed the 100km this past Saturday to obtain the special edition jersey. I paused the workout several times to refill water botles and to stretch and walk around. The first time, I came back and my HRM was no longer offering a reading. I stopped the game and hit the “paired devices” screen and noticed that the pairing to my HRM was gone. Re-paired it and continued on with my ride.
I stopped a couple of other times and no issues were noted. The next time, II stopped, I came back and my avatar did not want to move at all. Once again, I brought the “paired devices” screen and noticed that all of my devices (HRM, power, cadence, speed) had unpaired. Re-paired and my avatar started to move again (very scary, especially on a 100km attempt).
I have a theory that the unpairing may happen if there if I pause the workout for more than 10-15 minutes. I will try to test this again to see if this is the case.