Enduro 2 hangs (freezes)

My Enduro 2 (SW version 11.28) has the following problem: 

It freezes and becomes unresponsive.

This behaviour is observed twice so far - once using the stopwatch and once using the strength activity. 

The watch hangs for about 10-15 mins and the resets by itself (I guess that there is a kind of heartbeat implemented). 

After the reset it shows the last activity that was used for (paused in my case, but I was pushy with the buttonses) 

Additionally occasional power drains are also observed - meaning the battery dies within two days after it was fully charged (even though no SW updates have been performed). 

Anyone with the same or similar issues ? What is your cure ?