Mine's the same, I always blamed the broken rings in Cyl 2 but it still happens after my re-build/re-fresh.
Buggered breather tower valve I think was mentioned on here.
The crankcase has to breathe and it's got hot oil sloshing around in it, not surprising some comes out if the tower valve is shot.
New towers are expensive so it's time for a catch tank for me too.

'86 1.9 DG, 4 spd, tintop, camper conversion.
Split case club member.