I run this thing side by side just to compare and check it out and its close.
Both share the Cadence, RPM and chest HRM sensor. So nothing to see there.
I got 35 more calories from the F5.
I dont know much. What do you see that is alarming?
https://connect.garmin.com/modern/activity/1642290380
https://connect.garmin.com/modern/activity/1642287566