I've had the same problem Red. First couple of times I put it down to having used pattern seals. Last time around i ordered Yamaha seals. Thus far they've been fine, done probably 300 miles or more, some of them on a track day. noticed yesterday that the same seal is now, once again, causing a slight misting on the stanchion.
Probably going to have to get the forks re finished over the winter. 😔