Forerunner 255 Series and 955 Series: Cannot edit heart rate zones percentages

Sure. Lucky YOU :). But for "only" one activities there are many other options- cheapest and with less "tamdaradam!!!" marketing tricks. As you say - It's tough. And sad.

Cheers

That a leading company like garmin takes more than two months to fix something that is essential for the use of a high-end sports watch, is not correct, it gives a very bad image. Other newer companies like coros is a wonder how they update and how well it works all the part related to running (detection of threshold pace, heart rate, native training by power both from the watch itself and from stryd, training by pace zones that Garmin still does not have it, etc).

I went back to garmin because I like all the health, stress, body battery, hrv, etc, but these basic problems, the time they are taking to fix it and the little information they give, is not worthy of a great company. It is normal that we are angry. It's 650€ for a faulty product (defective).

Ive tried that but maybe Im doing it wrong . I want to customise each HR Zone with the below so Im going into Device > User profile > Heart Rate Zone > Zones> and setting them in there based on BPM & then Synch  , Ive done this about 10 times but it always ends up changing back to % of heart rate , rater than the "BPM" option  ive chosen 

Z1: 110-140
Z2: 141-152
Z3: 153-160
Z4: 161-171
Z5: 172-200

Mine also goes back to % HR, but when I change it to BPM, the values I put in there remain, so I know they've saved.  They also are reported correctly in my activity stats.

The "Based On" setting is I think irrelevant - it just gives you different ways of entering and displaying the zones.

Mine also reverts back to %HR after i have started an aciticity, even though its set to "based on bpm". Another bugg i guess

But are the values correct when you change back to BPM?

Yes.

but shouldn’t the values be correct thou then when I do an activity. This is my run this morning and the BPM in each zone isn’t what I set them to be

So the only real bug is this control not keeping track of your preference.  There's nothing really stopping the editing of the default HR zone.

Have you deleted all of your sport-specific HR zones?

This is how my HR zone screen looks.