Unfortunately the angled ballcups aren't designed for the inner rears and that is most likely the issue. They are designed for the outer rear to give extra clearance for the rear wheels, not for BB clearance. They will hit the dust-cover under compression and cause problems.
Here is a quote from the website and press release "Included is an angled version of the Wedge which can be used on the outside of the rear camber link for increased clearance on the rear wheel"
Website update.
Sorry you had some issues with the inner ballcups popping off, but maybe give them another try with the normal straight ones inside.
here was PW's reply on this tread.