Embassy ONEX - Domestic Hot Water not flowing

We have had several lockout issues and ignition failure events. Mostly in the summer months. Unit has been serviced yearly. Lately we have been having DMH issues where the water runs cold. The unit displays "D" with a temp around 50. (DMH set to ~130). It will stay in this condition as long as the tap is open. I've had to Power cycle the unit (sometimes twice) to get it to reset and work. I have tried turning the DMH to the "off" position for up to 1 minute and then back on but this does not correct the issue. I'm thinking that there may be a faulty scald-prevention valve or controller. ?? (And I'm not happy with my local service rep. If there are any more technically astute service organizations in Anchorage that works on ONEX I'd like to know). The one I currently work with starts with an A and ends with an A.