This is not too unusual, and not always easy to get rid of. The first thing to try, is to (1) make SURE you have the plane trimmed for hands off level flight, as any pitch in level flight will be magnified in knife-edge, then (2) try a stretch of knife-edge using ONLY enough rudder to hold it in position. A well-trimmed pattern plane that will knife edge all day long can be made to pitch and/or roll with a huge amount of rudder application.

If this doesn't help, then moving the CG so that you are a little more nose-heavy may help. This will require a touch of up elevator to fly level, and that may be enough to straighten out the KE flight.

I am not big on moving the ailerons either way of a true center, as it messes up your airfoil, with undercamber one way, and reflex when inverted, or vice-versa.

There is some other "black-magic" approaches that I won't go into, as they mess up other maneuvers. The best way in this modern era, is a computer radio with some mixing capabilities which will allow you to correct any such problems in just two or three flights.

Clair