16x risers not working

[FlyingFree333]

I have several rigs with ASRock Killer MBs, they have 3 16x slots and 4 1x slots. The 1x slots, with shorted pins, work fine with 1x-16x risers. The 16x slots with 16x-16x risers only work if no risers are being used in any other slots, otherwise Windows device manager reports that the resources for the card are in use and the card remains disabled. Any ideas?