Power steering hoses and reservoirs are crap on all BMWs. I have E30s, E36s, E39 and X53 with leaking/seeping hoses or connections. Mine were leaking and I replaced the two to the reservoir and that seems to have stopped it. Maybe take some pictures of where you're seeing it. I did all my valve cover gaskets, seals and o-rings and that seems to have ended the oil leaks…for now.

__________________
Daily Drivers:
- 2008 535i, 320,000km
- 2004 X5 4.4, 01/2004 production, 420,000km
- 1997 328i, 350,000km

Track:
- 1996 328i, track/race car, ~300,000km

Winter:
- 2013 Ski-Doo MXZ X 800 E-TEC, trail can
- 2007 Ski-Doo MXZ Blizzard 800 HO
- 2001 Ski-Doo MXZ 600 w/800 engine, exhaust
- 1978 Ski-Doo Olympique 340 (vintage race sled)
- 1977 Ski-Doo Olympique 340E