Nextbox stops unpredictable

Since about one year I am using Nextbox. I purchased this device to get an easy to maintain cloud solution. In fact, I am only using files, calendar and contacts, nothing special.

From the beginning the box stops working in average every 3 - 5 days. Mostly during the night. I then do a reboot (via SSH) and the box works as designed. Several support cases led to no solution. Since I am not the OS hero, I am unable to dig very deep.

Is there user, who experience a similar issue?