Garmin Forerunner 955 reboots over and over again

Hi, 


During my swim activity my watch started rebooting. 
At this moment the watch reboots over and over again, without an actual completed reboot. 

I've tried the normaal on/off procedure but also the factory reset option (with all the button combinations).
I've tried to link it to charger of computer, without any succes. 
Watch always follows the automatic updates it receives from Garmin Connect.

How can this problem be resolved? 

Br, Dieter