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Sailboat Anahi

I have looked but cannot find a similar issue on the forum.
Axiom 9 and 7, (9 is Master) wind, and speed instruments via ITC5 and NEMA 2000, depth direct to Axiom 9 (installed in November 2018 by dealer). Raymarine ST6000 autopilot on NEMA2000 Vesper Marine XB8000 AIS sending data on NEMA2000. All systems working fine.
After February update of the Axiom I woke at anchor one morning to find the Axiom 7 stuck in boot screen. Shortly after the same happened to the Axiom 9. So no chart plotter, depth, wind or speed available to navigate back to safety of a marina. I was anchored off a small island east of Phuket Thailand.
Once back in the safety of a marina. Started investigation.
Recycled power and both MFD still in boot screen. Recovered by factory reset. However after a few hours same happens. Numerous attempts made.
Dealer removed both MFD and found nothing wrong.
Re-wired all 12vdc supply to separate supplies through a dc/dc converter in case fault was due to noise. Still encountered same issue.
Powering up the system in a certain sequence allows the system to function normally. Cold Boot up (12vdc turned on) sequence AIS, Axiom 9 then Axiom 7. In any other sequence MFD fail to boot screen after a few minutes. Indicators of failure are depth going erratic from 4M to 390M+, GPS signal lost. Same issue with soft (turning off at MFD 12vdc supply still on).
I am now very good at factory reset and rebuilding the preferences of the Axiom.
April update installed and now both Axiom fail to boot screen regardless of power on sequence.
AIS removed and tested by dealer. No faults found. Dealer changed NEMA200 network supply cable but system still fails after a few hours.
Finally I (yes I and not the dealer) went into the AIS system and turned off the NEMA2000 outputs except the AIS data. NEMA2000 inputs into the AIS not inhibited as I use the data across the AIS WiFi system to other displays. Since then the system is stable with numerous restarts tested. It took nearly 6 weeks, considerable inconvenience and extra financial outlay to come to this resolution.
So one question is why The NEMA 2000 data from the AIS, which is repeating the AXiom data, cause both Axiom to fail to boot screen?
Second question is can I trust my Axiom MFD to work reliably when sailing remote locations or should I have just stuck to paper charts, wet finger and a plumb line?