I did not the head job yet, but i think i know what happened. the head was drilled around the sixth cylinder, in order to get better lubrification at the end of the engine. a machine shop did that a long time ago. a pipe was shunted from the oil sensor directly to the head. this pipe broke so i removed it and put a screw with silicon type gasket . I think I put it directly on the screw : it went away and slid directly into the head. that's the reason why only one bearing melted. so it's a headjob again and one good lesson for sure
