HR Zones - "Based on" Setting changes after run from HRR to HR Max

Hi all, 

i have set on my Fenix 8 in User Profile the Zones Setting to be based on "%HRR" . Both the Fenix 8 Menu and the Garmin Connect App show this setting

After a run - i realised that the setting changed bac, to "%Max HR" . 

Whats the trick to keep it set to HRR ?

Cheers, Max