some of the BMW plugs are notorious for looking snuggly latched but in reality not fully engaged. over time, with engine vibration and road bumps, something may have come loose...

the other possibility, a wire that was once properly routed, was dislodged from its path and now is shorting to chassis or interrupting the line...

of course, there is a possibility that items that you have replaced may have failed again - i recently replaced a collant tank that was leaking at the seams with a spanking brand new OE tank from a dealer, just to find couple of days ago that the new MF!!! is leaking at the same seams... and that was a virgin original tank!!! of course i will replace the newly leaking tank, but WTF?!, i bought that new tank in May, and less than 3 months later it is pissing my coolant away!!!!