Not sure which seal that is, but I've had good luck with clearing up little leaks like that on mine (one PSS and one something else about like it) by making small adjustments to the rotor (the part attached to the shaft). Sometimes more preload of the bellows (think of it more as a spring). is not exactly better. They all have a "happy spot" that they like to ride. Like lively said, check for debris or damage to the surfaces. Has your alignment been check lately?
Korey Morris -
Sold to Arkansas: 1986 Supra Saltare
Current: 2018 Moomba Craz