OVMS keeps going offline

I’ve had an OVMS module for around a year and it has worked reliably. However, I am recently finding that it keeps going offline and power cycling the unit usually brings it back online. My car is a Nissan Leaf Tekna 2014 model. Is it a hardware or a firmware/software issue? I have set it to auto update the firmware so is it possible it has done an update which has introduced a bug? Has anyone else had this problem?