Getting extra primary trigger signals - can filtering help?

[SPatrickB]

I have developed a problem with extra, close to actual triggers on the primary trigger input at ~3000 RPM. This presents to the ECU as a sudden increase of RPM from 3000 to ~8000 and so hits the limiter and produces errors about secondary. However, log (at http://www.vems.hu/files/PatrickB/TriggerErrorProblem/) show secondary is OK. I don't know why this happening and so would like to filter it for now. I have enabled the RPM filter but it doesn't help (the name indicates it should though, but I can't find doc about it).
Any ideas if any filtering can help?