That could be down to over enthusiastic spline lube or the clutch carrier O-ring worn out.There is oil all around the bell housing, I guess it's the crank seal. I'll find out when I next get a chance to play-got some actual work to do now.
The O-ring does become less elastic with age and it's job is to make the final seal between the clutch carrier and the output/balancer shaft.
Cheap enough to replace but a bit fiddly (the clutch cover screws, washers and the centre lock-nut and spacer are supposed to be replaced each time they're disturbed.

