Last week it was found that the compression of the 850 was bad.
compressietest
Just inspected the engine with an endoscope from work. Not good news because the second cylinder had "snot" on the wall, the third looked like a dripstone cave; the first and fourth were reasonably clean. So I am thinking of a broken head gasket between the second and third cylinder. We'll disassemble the head soon and see if more misery surfaces.