It appears to me that Connect is not consolidating HR readings from multiple sources.
Scenario; I have a Fenix 7 and wear it 24/7. I use it to record HR while running, either using the built-in sensor or supplementing it with a HRM Dual. The daily HR graph on Connect clearly shows the HR measured during my exercise.
If, however, I'm cycling using Tacx, with the same HRM Dual but that connected to Tacx, then I upload the activity to Connect, then the Activity stats correctly show my HR, but they are not replicated in the daily HR graph. If I check my Fenix 7 while using Tacx, the HR shown is far lower than being recorded by the HRM Dual (typically 75 instead of 145). It is this lower figure which appears in the daily graph.
The example below shows both a run and a couple of Tacx rides on the same day. Note that the HR recorded during my Tacx rides is nowhere near the 140 or so it should be.
It looks like I may have to dual-record my HR while using Tacx, recording an activity on my Fenix, then delete that activity?
Once I have that corrected, I guess I should also see what's happening if I go outdoors to ride using my HRM Dual connected to my Edge 840.