Todd sorry you having issues the M55 has actually been a good unit. The air draft if its an insert with a liner, Enviro suggests a setting of about 1/2 inch of the lever exposed out of the hole. Depending on the pellets you are burning too, air shutters can be more sensitive. With good pellets, 1/2 to 3/4 inch out is a good setting. For free standing stoves, I can't remember if damper setting arm or a handle. For Flashing 3 that is proof of fire. It usually means the exh path temperature has cooled down and POF sw opens, and shuts down stove. Couple of things to check before replacing. Remove it and see if buildup on the switch especially dark nastry coating, creosote. If so, prob pellets are running cool. If switch is clean or lightly coated, it could be a switch, espec if it happens on low heat settings. If happens on high heat settings, and switch is dirty, then pellet quality is questioned. The convex blower on higher heat levels stripping too much heat off heat exchanger and cooling down exhaust path, I know its a weird thing, but we've seen that problem with pellets here in CT (last year was moreso than this year so far). Good luck, stay with it, you made a good choice.
Stovelark
Enviro EF3 FS pellet
Enviro Empress FPI AC
Enviro Kodiak 1700 FS wood (burning now)