W12 Ignition oscillators / cylinder failure / engine damage

Hello W12 friends and specialists.
My W12 from 2007 causes problems for the first time at Km-Stand 340TKm.

Error description:
6 cylinders no longer run, fell out while driving, engine lamp started to flash yellow. Short error selection resulted in cylinder 1.2,3, 7,8,9 "Zündaussätzer". In addition, a sporadic fault lamda probe.
In addition, we have a squealing noise when running the engine. Appears to come from the right cylinder bench (direction). That's what worries me the most. But then why "extinguishing" and why do these many cylinders.

Already excluded:
My first thought was to renew ignition coils + spark plugs. That was unsuccessful, however, no improvement.

Note:
Oil change new before 1,000 km - 5W40 was filled, instead of 0W40.


further assumption:
Somewhere there was something about a small oil sieve in the engine, but the engine had to be completely out because it was on the back side (splash wall). Eventl. Is this due to the thicker oil and the squeaking stirs from the then bad lubrication ?

Please dear friends, no wild speculation or useless comments. I'm looking for expert advice from experienced W12 specialists to narrow down and fix the problem. Has anyone already had the problem with their W12 or even fixed it on a W12? Is there any information about this "seven"?

Greetings Joe