Invalid PR detected

It's the second time this happens to me so maybe i'm doing something wrong. The previous  was on a 10k PB, both activities were on version 20.29. I don't remember having this issue in the past.

I'm setting a target (in this case it was 5k @ 4.20 ) and start running.

After the 5k auto-lap screen, i get the "target achieved" screen saying that i was faster then the target. During this time i cannot stop the activity.

After i stop and save the activity i get the message that my new PR for the 5k is the total time of the activity.

It's easy to adjust manually, but still annoying.