It's simple. You get the 5 units out of the 10000 fielded units, replace 'em with known functional units, and set up a test for those 5 units, cycling power (you said the problem was that they had to be reset several times to start properly, right?) for, perhaps 10 million cycles, and record the system response with your logic analyzer, examining the signals and comparing with what they should be. If after 10E6 cycles, which can be run automatically, you haven't found the "problem" then it's likely you don't have one.

The startup takes in the region of 15 seconds so my customer would have to wait 1300 days for me to 'diagnose' the problem. Your customers may (I doubt it) be willing to wait for so long, mine are not.

Of course I did, who knows how many, power cycles and saw NO failures. Thay you in your little cocoon have ideas about what I will see when doing what Richard does (he has the time, evidently), does not mean that 15 seconds times ten million is even moderately possible. Yes I have an automatic power cycling thingy and it was used to no avail. Maybe YOU tell your customer and your service techs "you think you have a problem, I will tell you you do not" I never would. Thus I fixed the problem (albeit in a way that does not meet Richards approval) and shipped. Had the problem persisted no customer would have been any worse off. However, what I did, based on experience, not Richards 'advice' took care of the issue.

If you wanted to do your job, Erik, you'd find the problem and fix it.
Saying that I do not want to do my job is an insult. Evidently whoever uses supervisors is not doing his job according to Richard.
FYI I AM doing my job, I fixed the problem

I'd venture that the "real" problem is too much capacitance on Vcc and too little heft in the off-board power source. Now, I haven't observed the problem either. I bet you don't know what the risetime of Vcc at the MCU is, either.
You can 'venture' all you want, I fixed the problem, re "too little heft in the off-board power source" it is a 1000A cold cranking 24V lead-acid battery that, of course, might not be "hefty" enough for you.

Erik

PS I know that by now you are about to wet your pants because you are losing the argument about supervisors, but if it is that hard, we'll keep going toil you finally can accept facts may that make you have a nice warm feeling for a short while or not.