Suburu Legacy cam shaft seal won't stop leak

Suburu Legagy Outback, 2.0L, 1999, 175K+. Overall good shape and has always been well-serviced. Seals have been leaking. General mechanic successful replaced all and timing belt, but the new driver’s side rear cam shaft seal won’t fit well enough to stop the leak. He tried a stop leak overnight and it didn’t help (I thought those had to be driven in to work?).

If a replacement seal is properly installed yet continues to leak it is likely that there is a problem with the camshaft. Possibly a rough groove worn on it or enough slack on the adjacent bearing to allow the cam to wobble. Sometimes the leak is at the outer circumference of the seal caused by a burr in the seat. A different brand seal might improve matters. Dressing the outer circumference of a new seal with gasket sealer sometimes does the trick. Sometimes it requires pulling the head or living with the leak.