Big-time Mag Drop

Abbreviated session with plane today.  Carefully inspected all visible wires for chafing, breaks.  I wanted to eliminate the panel switches as a possible factor so ohm testing and inspection of connections on that circuit showed all was well.  Started engine and experienced big RPM drop on the new (second replacement) module.  Dropped from 2,400 warm up RPM to less than 1,000.  Shut it down.

Seems to me we have two good clues: module test OK with reinstallation of old (1,000 Hour) module; and, until today, big drops with new modules were only AFTER flight.  OK preflight tests until today.  Rotax eccentricities aside, I'm looking for some kind of wire abnormality.  Maybe heat or vibration in flight is an issue.  BUT...none of this squares with the no-issue performance of the reinstalled unit in troubleshooting earlier.

I will plan on a long day tomorrow with the Heavy Manual troubleshooting and will report any pertinent findings.  If Roger or anyone else has thoughts on what I might look into, please pass them along.   TIA       Jim