same as the forks on the B40 Im working on.
one drain screw has sprung a leak , no pressure on it as bike on a stand with wheel off the ground, new washers, it just happened one weekend.
the fork leg seems to be a welded assembly , a seam might have sprung a leak, or another possibility, being split caps is that a tapped hole may be too deep and broken through into the fork oil chamber. Both of these could be aggrevated by movement and vibration.