Indoor Rowing - Heart Rate tracking locks in

Anybody here using Garmin Indoor Rowing app? I have issues when the watch (both F5 and my gf F5s) locks at very low HR, say 85-100 even when I can barely catch my breath. I know there are a lot of conversations here pointing out that the watch has to be in proper position relative to the wrist etc. But this issue mostly happens for indoor rowing, so I'm wondering if this is specific to this activity app. I think I wear it correctly. It's really annoying as it takes sometimes 10 min until it starts showing the "right" data. I usually try to pause/resume the activity, take the watch down, wipe the sensor etc. etc. Didn't notice which of those really helps it to catch up, it does this eventually, when I give up and just focus on rowing :).