@Dimitrios-Kanellopoulos I will now proceed as you suggested !
It was with the default “trailrunning” profile of the watch, and further tests I did just now have the same result. What I tested:
Start Navigation in options, then interval after the start of the activity
Start Interval in options, then navigation after the start of the activity
Star nothing in option, start on, then the other after the start of the activity
One random test in running default mode
One random test with MTB default mode
Sooooo, I conclude that…well I was right at my first post !
Well, that could be a feature idea for Suunto developers haha 🙂
Anyway, thanks guys for the help and feedback !