Note: all of the issues below are fairly new. I haven't had any of these issues prior to the 11.28 update.
1. Wrist HR used to work acceptably well last year. Now if fails to work properly on 100% of runs, for large parts of those runs, producing unreasonably high HR that I can't possibly have. For example, in one of my recent runs it tracked me in the upper part of Z5 for 30 minutes, all while I was running easily downhill breathing mostly through my nose.
2. The abnormally high HR from the wrist sensor makes my watch "autodetect" the new maximum HR, which is absolutely unreachable for me. I am 52 years old. Believe me, I don't have the max HR of 186, especially not the one that was detected on a very easy run.
3. The new max HR results in auto-adjusting my HR zones even though the zones are based on LTHR%. If it is based on LTHR% that means it must not change unless the new LTHR is detected! What's the point of having it LTHR based then?
Here is how I found my LTHR% zones auto-adjusted by the watch:
Based On: %LTHR
Z5: 105%-114%
Z4: 99%-104%
Z3: 93%-98%
Z2: 83%-92%
Z1: 67%-82%
Isn't that ridiculous?
Furthermore, I I clearly remember configuring my watch to not auto-detect the max HR, but it seems that has been ignored in the last update.
According to https://www.garmin.com/en-US/garmin-technology/health-science/heart-rate-monitoring/:
Compatible Garmin devices can automatically update your maximum heart rate using your performance data. If a heart rate higher than your currently set maximum is identified and passes a reliability threshold, your personal maximum heart rate is updated on the device or in the Garmin Connect app.
This feature can be turned on or off in the Physiological Metrics -> Auto Detection menu of the device.
Guess what, there is no longer Physiological Metrics menu in my watch after the last update, and no Auto Detection menu that I can find. It seems Garmin has decided that it should simply be turned on by default for everyone.
And someone please tell Garmin engineers that there shouldn't be a 1% gap between zones. Zones are supposed to be continuous.
4. Unrealistically high HR results in negatively affecting secondary metrics like Performance Condition, Training Load, Recovery Time, VO2 max. Bad data in - bad data out.
5. Sleep tracking is completely ruined too because my Garmin now thinks that I sleep when I work at computer. And it replaces my night sleep with this short fake daytime sleep. I don't really care about the sleep tracking, but that destroys other training and recovery metrics such as Training Readiness. What's the point in Training Readiness if all the raw data is useless.
Again, all of those things used to work quite well until Garmin has "improved" them. Has Garmin heard about beta testers? Not throwing half baked beta builds at users hoping that users would catch bugs but real dedicated beta testers who deliberately look for bugs. Also even when users report bugs in the beta software, it seems that Garmin just shrugs and releases the half baked updates regardless!