Hey guys, to help give some insight to this issue, there was a time period when BMW produced the E39 5 series and that vehicle chassis was built with a hub that was 74mm compared to the std 72.6, at that time even though the chassis is different from the 3 series, many wheel suppliers for BMW built all the base wheels to a 74mm C/B because it was easier to ring down than to expect customers to go find a machine shop to open the bore. Typically what does happen in many cases of swapping wheels, is the ring can get stuck inside the wheels coming off, or pop out once they are laid flat on the floor and they can be misplaced once they have been moved, or the ring could be seated to the hub and the new wheel has the correct bore and simply not sitting on the pad all the way?? The ring is a very thin ring.
Also with other aftermarket brands, many companies that build a wheel with a similar PCD and offset also will produce the wheels with a similar ring package, it is best to check with the manufacturer. In the case where you took off aftermarket wheels to put back on stocks...the aftermarket most likely took a ring and it was lost, or is on your hub causing a vibration with your factory wheels because they are not seated to the mounting pad.
I hope this information is helpful.
Jim