what method was used to check the timing,
common issues are chain stretched or vac pump pails pulling the exhaust cam to a stop and chain slip but that tends to bend valves when happens, another issue can be the oil control rings in first journals on camshafts engine running and hot open oil filler and f can see oil being sprayed across from them they are worn or snapped, believe to be a updated part from bmw now made of nylon same as oil control rings on pistons,
another common thing is bottom gear sprocket wears and feathers off until chain slips,
common issues are chain stretched or vac pump pails pulling the exhaust cam to a stop and chain slip but that tends to bend valves when happens, another issue can be the oil control rings in first journals on camshafts engine running and hot open oil filler and f can see oil being sprayed across from them they are worn or snapped, believe to be a updated part from bmw now made of nylon same as oil control rings on pistons,
another common thing is bottom gear sprocket wears and feathers off until chain slips,