I've seen this on the E60 forums. Not sure the cause though. If it's your last shot, not sure if welding it up would work. Some pictures might help as I'm not exactly sure what you have to work with.

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Daily Drivers:
- 2008 535i, 290,000km
- 2004 X5 4.4, 01/2004 production, 380,000km
- 1998 328i, 370,000km

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

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