I did a 40 minute run in zone 2 this morning, and my v02 max went down from 51 (23/7) to 49 (see attached images). And the suggested recovery time was 27 hours!
My sleep score was good, my body battery was good, and the effort for the workout was 2.5 and 0.0 (so nothing wierd there). My training redinnes is back at 79 already, but there is still 21 hours remaining on the recovery time
This must be some kind of bug, right?
Nothing changed on your zones? Max HR setting still OK? VO2Max is a moving average. Did you have troubles (less training, fatique) in the last weeks/months? I am not sure HRV does something to the analysis. You could have a stable heartrate during the run, but with a HRV that suggests some tiredness. Maybe something like that influences the score of your run. I am just guessing here, look at the upcoming runs. If the look fine, don't worry to much 
