Wrong Training Readiness after 9.20 software

V.Stryker said:

Alternatively, I also experience an anomaly in the heart rate zones during training.

I see no anomaly on the screenshot. Having spent 83% in the zone 4 does not mean there was any anaerobic load. By principle the body cannot sustain working in anaerobic mode longer than couple of tens of seconds, so if you've spent half an hour in the zone 4, it was no anaeroby, otherwise you'd be dead. To get some anaerobic effect, you have to do repeated high intensity short intervals (best result with couple of seconds up to 1 minute or two per interval). More details here: What Is the Training Effect Feature on My Garmin Device? | Garmin Customer Support