From Rotax Owners Forum, Mike Miller
"It’s been my experience the 965349 regulator fail from vibration. The potting compound is not rigid, think of the PCB as floating in jello (not sure if jello is a thing in Australia,) the PCB is held to the case by the eight wire leads of the rectifier and SCRs. The typical failure mode is a low voltage alarm at low and moderate RPMs (half wave operation) or no output at all. Typically it starts as an intermittent problem that worsens over time.
Usually these regulators are easily repairable. The potting compound can be removed cleanly with simple tools and minimal effort. The picture of potting compound removal sequence spanned less that 10 minutes from start to finish, but I’ve had a little practice. Inspect the eight locations in the second photo for broken connections and re-solder as needed. The SCR leads may look ok, inspect them carefully, often they can be lifted off the board with your finger nail. The rectifier leads should have a cone of solder up from the board to the cut lead, what you usually find is a crater of solder with the disconnected lead coming through the center. If a lead falls off as you solder it, that’s an indication the failure point was at the body of the component and it won’t be repairable without replacing that component, I’ve only seen this happen once. If you we’re successful and removed the potting compound in one one piece, you can resecure it with RTV, after confirming it’s fixed." 😈