Forerunner 45 will not measure/save pulse nor distance

Trying to keep it short:

My Forerunner 45 with operating system 3.10 will not measure/save pulse nor distance, even though logged on to GPS/GALLILEO before hitting "start" button and run.

This is already my second F45 and after hard reset it works for some runs and then stops again.

Any solutions?

Kind regards,
Henrik (Denmark)