I lean toward the ignition being the culprit. I have a backup 3W ignition with the exact symptom. My suggestion is to get a CH unit or RCXL, either way CH sells them both. Piece of cake to mount a CH unit where the 3W ignition mounts and change the timing. You'll spend months sending parts back and forth to Cactus and not get anywhere. A phone call and a few days later you'll have it singing again. CH ignitions wear out too, none of mine last much more than a year/maybe two, (3-400 flights) before needing work, but when I send them to CH they fix them, charge me whats needed $ wise for the repair and about a week all told later I'm flying again. Usual repair is replace the coils and the spring that contacts the spark plug. Keep your 3W for a backup but just don't trust it. They love to quit working at the worst time.