I've kind of hung of mentioning this but the gubbings of a pro 2 , evo, bulb or anything are pretty much tweaked to each hub and arent interchangeable in any way. Its the transfer of the clamping force being directed down the center of the axle steps and middle of the bearings only work if the rights bits are in place. Otherwise it might lock up.
Had this problem with a bulb before by mixing up the correct internal spacers when building a bulb rear. Reported as locked solid when clamped.
If you change about anything like trying to fit a pro 2 axle/bearings/spacers into a bulb, it might not work at all :?