Nice pictures. Good Quality. I think I understand what you are describing but I'm not sure what you need. While you make a reference to detailed ISO tests, I don't think many people will know which tests are required. Perhaps you would be so kind as to share that detail so we can offer suggestions.

I am wondering also if you have an electrical engineer helping with this problem. Perhaps it is someone fresh out of school who is not familiar with the circuit as yet?

You have gone to a lot of effort so don't give up. Try to answer as many of the questions so that we may know how to help.

The question that remains is...what is your question? It sounds like your excitation system isn't doing what you expect. Is this a new or existing installation? Did it ever work properly, were any changes made or maintenance performed before the problem occurred, and (of course) was the manufacturer contacted? Once you let us know the exact nature of the problem we will be in a better position to possibly assist you.

Please pay special attention to screening, cable dressing, earthing/grounding. Over a period of time, we find after maintenance, all the screening plates/covers not put back in place. We may even find many screws missing. Making jigs to test various cards are doable but requires time/skill and will be expensive.

Conducting a thorough electronic component testings as part of a "live preventive maintenance" tests on an ongoing operational or running system is very dangerous.

IMHO the best approach you can implement is to conduct a series of thermographic scans on all the different sections /components of the system during 'normal operation' and use that as a baseline info for future reference. Scheduled follow up scans can then be implemented to predict for any abnormal deviations that may pre-empt impending component failure.

You asked essentially the same question (or at least very similar) about 1-1/2 months ago, with some of the same photos. Did the answers at that time not give you the information you needed to troubleshoot this problem? For diagnostics of specific electronic circuit cards, your best resource is the manufacturer's technical support personnel. Call them.