Agree with the rocker assy bolt(s) at this stage, but believe that the cam/lifter was the cause of the initial ticking. "tightening" by a non-MB familiar tech will result in the bolt holes being stripped. I think the required torque is less than 15 lb.ft. I had to do 3/4 of them in a replacement head from an outfit that had "international" in their name. The international didn't include German
It had about 6 that wouldn't hold on the bench test, another group that just looked bad, and group "c" that didn't hold at final install. The kicker was the instructions that actually stated that a "heli-coil was something that anyone can do". I didn't argue with that, I just didn't take if for a huge hint.