This is just a shot in the dark. Is the outer pin hole plugged where you put in the oil. If so when it get hot it leaks around the seal not venting out the hole. Is the outer seal dirty or clean.
A lot of thing can go wrong when putting in a any seal. Most good shops should be able to install one since they have it apart. If they put in the wrong part number the first time and they they use that the second time then. Then you can see where that goes. Hub has a damage spot that is not sealing. The list can go on.
Did they put in too much oil
