I have no experience with this (being a helo-type) but remember vaguely that one of the kit type aircraft (US 1985-95) with canard had the same type of problem.
A fair amount of these were sold, sorry I don't remember the name either.
Try the archives at plane and pilot, sport aviation or private pilot.
As I remember it quite a bit of testing and troubleshooting went on to discover what caused the issue.
Hope this helps a bit