Still sounds like EMF 'noise' upsetting your RPM sensor readings that the FADEC is seeing.

Have you changed anything in your set-up that could have put a source of electronic noise anywhere near your RPM sensor lead? Those things a pretty sensitive when it comes to picking up any sort of interference. e.g. you haven't put a new Servo near the RPM lead? An extra Rx antenna (if you're using 2.4), or moved your 36meg antenna wire near it?

In short, have you changed anything from the configuration you used last time you had a successful spool-up? Swapped-out a component, added something new, moved anything around??

BJ