Thanks for inputs. The EZLs are inherently old so that may be an issue - however, even the "new" one I've just installed was made in 2003.

Battery is a new full size MB, much larger than the original MB battery.

Sunday 14th June update:

Checked all around diagnostic socket wiring, measured relevant earths etc. All appears good.

My only worry is the cheap-feeling brand new Beru plug wires. Similar to those that were installed (brand new NGKs) during EZL failures 2 and 3. Again, I had no trouble with older Beru wires installed 10+ years ago - WHY DID I CHANGE THEM AND BRING ON THIS MISERY???

So, the only thing I can do is get hold of a genuine MB set of wires and hope for the best.

And possibly get a new alternator to assure the smoothest current delivery.

Yes, I could find a true expert who could run diagnostics - oscilloscope etc - on the system to look for any voltage spikes that may be the cause of these repeated failures.

New 1200€ EZL now installed and car started from cold with its usual perfection. It’s like new!!!

I’m not going to use the car for a while as I reflect and plan.

Huh.

R