significant error in the heart rate settings of the Garmin Connect app

Ying said:

the five names below do not change accordingly

Do you mean the names "Warm Up (Z1)", "Easy (Z2)", "Aerobic (Z3)", "Threshold (Z4)", and "Maximum (Z5)" ? If so, then there is no reason why the names should change, when you change the base. The purpose (and hence the names) of the individual zones remains exactly the same, regardless which base you selected. Just the method to calculate them changed.

If you mean something else than those five names, then please elaborate.

Yes, the five names should change along with the selection.

I have to agree with Ying here, even though there are 5 zones in each zone system, the meaning of those zones differ in each system (with default zone range percentages). And this has been a problem with Garmin for years.

For example for me (MaxHR 171, LTHR 151, Resting HR 43), the zones systems give me the following zones:

If you look at the HR ranges for me, the zone 1 in the MaxHR based system doesn't exist in the others, MaxHR zone 2 is zone 1 in the others, and MaxHR zone 3 is zone 2.

Giving the same descriptive labels for zones in all the systems doesn't make sense, since the zone placement is different. Which is clearly shown in the screenshots. (Are they from iOS version of Connect Mobile, I didn't find similar in either Android or Web versions?)

The fit file contains the zones ranges and their calculation method, so Garmin could choose a suitable set of labels based on that. Or they could remove the labels completely, if they are unable to adapt the labels.

In my case, the labels are identical in all three modes (MaxHR, HRR, LTHR) - Warm Up (Z1) / Easy (Z2) / Aerobic (Z3) / Threshold (Z4) / Maximum (Z5),  and it makes sense to me, since the purpose of each of the five zones is identical, regardless which method you use. The fact that the absolute numbers may slightly differ, does not mean that their purpose changes. It just means that depending on the accuracy of the collected metrics, the results may differ. In my case (having rather reliable and verified values in Max HR / LTHR / RHR), all three methods give indeed practically identical absolute values:

Did you reset the percentages to defaults when you changed between MaxHR/LTHR/HRR? By default Garmin keeps the zones intact and alters the zone percentages from defaults to keep the zones in place (i.e., it doesn't matter which system you choose, you'll get your old zones if you don't reset the percentages to defaults).

I'll try later again. Now I am heading out. However, even if the zones differ more than that, their intended purpose remains the same: Z1 being a zone for warm-up, Z2 for easy exercises, etc, so I see no reason for changing their names.