High heart rate values after activity

Hello. I have a problem with the optical sensor on my 955 solar (sw 19.18). It happened a couple of times (even today after a light run) that after finishing the activity of running with a chest belt, the value measured from the optical sensor jumped to an extremely high value. today it was 197bpm but a few days ago 230bpm. Always after finishing the run. The external sensor was no longer active and I turned it off just to be sure, but it didn't help. I also turned the optical sensor off and on and it didn't help either. A soft reset of the watch helped.