Peculiar bug. Yesterday my wife did her first max effort 5k run in a long time, as mostly a Z2 runner, and a relatively new (3 months) Garmin user.
Her Max HR automatically adjusted from around 180 to 190. Looking at her stats, this was not acknowledged in the output--so her zone calcs for zones 1-5 were still based on the previous HR setting.
As a result the run was depicted as being 95% zone 5, with her zone 5 lower limit being set at >163, which is 85.7% of her Max HR, despite 90% being the metric default for Z5.
In addition to the zone metrics, I believe this also had an effect on other metrics like Training Effect (5.0 Overreaching) as well as Training Readiness, which pinned at 1%.
If the watch can detect a new MaxHR, it should also be able to retroactively apply that new limit to the current effort.
Thanks