Yup. My guess is that the cores they started with had grooves in them from the previous seals. So the rebuild shop (Epi, Cardone, Dorman, etc.) turned the seal surface down a few thousandths, and ta-dah...now they're too small. Another possibility might be that they turned the actual bearing journal, and if that's the case...there is too much clearance between the roller bearing and the snout of the half-shaft, and its wobbling around. The seal cannot flex enough to compensate for the extra clearance. In either case...if you still have your GM shafts, throw a mic on the journals and the seal surfaces to compare the GM shafts to the re-man shafts. I would return the shafts if they are a sloppy fit. Any counter guy worth a damn should give you an exchange or refund if that's the case. Take your mics with you so you can check the snouts at the counter...and keep pulling them until you find a pair that is within your spec (often a tighter spec than the rebuild shop).