(the bolt to the center-left holding the oil rail to the head)
(a closer look at the bolt in question)
(My botched attempt at drilling a hole through the bolt...but it'll hold regardless)
(I used some stranded copper wire to secure the banjo bolt to the oil rail.)
I forgot to take a picture of the fix, but this will hold until I do the whole engine rebuild this winter.
Bottom line: The M30 engines of this design should all be checked for loose banjo bolts. What happens at first is oil starvation to the rear rocker arms, accelerating wear. But the worst part is, should the bolt come loose, it could cause catastrophic failure to the entire engine!