It is possible to damage the seal when installing a new axle. Either the seal itself was damaged or the spring on the back side of the seal that tensions it to the axle was bumped off. You will have to remove the axle to change the seal obviously and it is not too hard to just replace the seal but they can fight you breaking them loose to pop out. I use thick wall metal pipe that is the exact size of the OD of the seal to install the new ones.