It’s not directly openHAB related, I hope that’s ok?
My Shelly BLU Door/Window was completely frozen (the software, it’s about 18°C in here) this morning. After much trouble (resetting, removing the battery…) the device suddenly worked again. Not that happened right after a reset or something; it was a mysterious miracle.
But now it’s frozen again… 
Does anyone have any experience with this issue?