@Turbo Listen ... I don't speak English well but I presented you my experience of my case where I wrote that I also did the continuity and isolation tests several times and they were always ok but your case is perhaps different.

Hi .... it also happened to me in a previous printer, I also changed the power supply only to discover that it was a false contact in the motor cables. I changed them directly even if measuring them several times with the tester (at that moment) they were always ok.
Now, I don't know if this could also be your cause but if you think it appropriate you could try it.

@Phaedrux Ok..... Only during a failure condition....

@Phaedrux Hi, maybe I say something not exact but I'm always looking for a solution by character. There is a value in the PID M307 which indicates the power of the heating phase which by default is 100%. If you decrease example to 80%, could it no longer give the warning? It might take a little longer to heat up but would you have other problems?

ok ... i solved. It was because of the config.override. I sent an M500, the file updated and the "Heaters x not found" errors disappeared. It remains the "warnig Heater 1 but I should resolve with a new pid.

Unfortunately I agree that I have the following errors:

5/10/2020, 08:48:48 M98 Pconfig.g
HTTP is enabled on port 80
FTP is enabled on port 21
TELNET is disabled
Warning: Heater 0 appears to be over-powered. If left on at full power, its temperature is predicted to reach 365C
Warning: Heater 1 appears to be over-powered. If left on at full power, its temperature is predicted to reach 790C
Error: Heater 2 not found
Error: Heater 4 not found
Error: Heater 5 not found
Error: Heater 6 not found

On Heater 0 and 1 I think I understand what it is (maybe even PID to be redone) but for Heater 2-4-5 and 6 what should I check?

@Phaedrux Hi, I loaded 3.1.1 and then the new config, home, etc ...... everything worked right at the first try! This is a satisfaction both for me and for you who have patiently supported me. Thank you again!

The PIDs remain to do and move the 3 Z motors but I will do it later when I have some free time.

In the meantime I ask what "Mode: FFF" means in DWC (top right)

I don't know if it was there before but I hadn't noticed.

The initial (basic) configuration with the configurator (excluding duex) was very useful for me but I find it much better to use the Gcode guide to make additions and / or changes. It is also easy.
Only the references to the duex seem to me (for my way of doing but maybe I'm wrong) a bit limited. I have yet to understand its logic.

@Phaedrux Ok, I get it, just motors. But to learn the command syntax for duex is it correct as I wrote above? How was I supposed to write?

Thank,
Sorry, I didn't explain. I only meant the gcode part with examples on extruder, fans, temperature probe, etc.