Apple Watch Series 7 recording unusual heart rate

Series 7 Apple Watch running 11.3.1, charge @ 82% overnight last night, reporting HR of 163BMP for several hours?

Way off normal!

This is the first time I've seen this kind of anomaly in the three years I've owned and used this Watch. When I work out on my indoor bike trainer I have to WORK to get my heart rate up beyond 140 BMP & that for only a brief period.

I'm nearing 76 years old, use 150 BPM as max HR for training and exercise routines. Resting HR typically averages 55BPM so the 163BPM numbers - for literally hours, according to this watch - just doesn't make any sense.

[Re-Titled by Moderator]