It's like the oem pulley is two pieces. The inner piece is firmly mounted to the crankshaft and in it's correct position. Then theres an outer piece that the belts ride on. The two seem to have become seperated and the outer part of the pulley is sliding on the inner part.
The inner part of the pulley is in it's correct location. The outer ring, that the belts ride on, is sliding in and out. When it slides out, it causes an alignment problem for the belts and they get thrown off.