Position of eccentric crank?

[FiatFan]

I'm having a problem with a LifeLike 0-6-0 switcher.  It will run ok in forward but when I go to reverse the eccentric arm moves out of position and locks up the engine.  I'm suspecting that possibly the eccentric crank is out of position.  On both sides of the engine the eccentric cranks are offset from the centerline of the axle.  The one that keeps locking up appears to be very slightly more offset from the centerline that the other one.  Where should the eccentric crank be positioned in relation to the centerline of the axle?  I've looked at images from the internet til my eyes are blurry and can't really tell for sure.  Some appear to be aligned with the centerline of the axle others not so much.  I always bring the engine to a stop before reversing direction.

Any information, suggestions, and/or guidance will be greatly appreciated.

Tom