If you want to input a certain zone limit in bpm for common heart rate zones (not by activities, but zones in general) it only allows you to enter a percent despite it being marked as "bpm"
If you want to input a certain zone limit in bpm for common heart rate zones (not by activities, but zones in general) it only allows you to enter a percent despite it being marked as "bpm"
HR Zones are handled by different watch models differently (even if you use the phone app). For example my Instinct 3 allows setting the values in bpm without any problems:

I suggest posting your concern on the subforum dedicated to your watch model, and also reporting it to the Product Support through their website at https://support.garmin.com. BTW, does it work correctly when you try changing the values directly on the watch?
Now it's been fixed somehow and can't be replicated anymore :) So it was a temporary bug I believe