I got frustrated and tore the wiring apart and reconnected everything once again. Ran the tests all over again.
Everything was 100% (just like before) except for that I got no response at all from the Z- end stop. I replaced the wiring for that end stop and it responded fine.

I started the printer and thought I'd try "home all" just for fun, before I did any testing. Eureka Homing works perfectly now

The only thing bugging me is that a faulty wire could consistently work in end stop tests, and just as consistently fail in homing tests...

@Veti Thanks for Your help and suggestions. They made me think twice about trusting some random post, instead of coming here for help.
It sure put me in the right mood to try solving this! It's greatly appreciated.

@Phaedrux Thanks for the links, I'll read them all through carefully when I get a little bit more time to spare.

@Phaedrux @dc42 @davea
Success
A big thanks to all of You for Your help and Your patience. It's greatly appreciated.
It's a bummer that I can't return the favor. At least not any time soon...
I'm officially retracting my claim in my first ever post on here, that I thought I understood the basics of how the Duet boards work.
That's clearly not the case, but I hoping to slowly learn as I go along in this endeavor.

I found a simple workaround. Just added the ip address and name in the hosts file in windows.
I have to do it on every computer I plan to access the printer from, but I only have this one and a laptop, so no problem

@Phaedrux @dc42 @davea
Success
A big thanks to all of You for Your help and Your patience. It's greatly appreciated.
It's a bummer that I can't return the favor. At least not any time soon...
I'm officially retracting my claim in my first ever post on here, that I thought I understood the basics of how the Duet boards work.
That's clearly not the case, but I hoping to slowly learn as I go along in this endeavor.

@dc42

Ahh, ok. I hope that's the issue. I've already done a couple of tests and it prints great.
If the display starts working, that's the last "hurdle" in my rebuild of the Mecreator2. For now that is.

The next step is to make the extruder all metal, so I can increase the temp and hopefully print nylon.
Maybe even PC at some point as I have a couple of rolls of that stuff.
If that works, I might try out a bowden setup so it can use all of the bed surface. Now it doesn't quite reach the front edge, due to the bulky extruder setup. An extra 5-10mm would be great for printing RC car bodies... I'll let You know tonight if things worked out

@Phaedrux
Downloaded the file here at work and thats the exact same file that I already installed, so I guess I did something wrong (go figure) when I installed it. I'll let You know how it goes tonight

@phaedrux
Ok, Thanks. I had already gone to bed when You posted and I'm at work now, but I'll do that when I get home tonight.
I reeeally hope that will fix it This time difference is a bitch...

@dc42
Well, I downloaded ver. 2.02a from here and installed it Without any errors. It had ver 1.something before and It now reports ver '2.0(RTOS) (2018-06-05b3' from the software information tab on the settings page. With M115 in DWC I get this:
FIRMWARE_NAME: RepRapFirmware for Duet 2 Maestro FIRMWARE_VERSION: 2.0(RTOS) ELECTRONICS: Duet Maestro 1.0 FIRMWARE_DATE: 2018-06-05b3
Do You mean that it could somehow be another version? Should I try installing the latest beta?

@dc42
Thanks. I'm sure it's going to work perfectly on Your Maestro just as it did on DaveA's though.
I'm almost certain that it's something wrong with my wiring or the Maestro itself. I just can't figure out how it can miss read the files and then respond with clear and readable text if the wiring is to blame, but I'll re check all that tomorrow. For now it's a printer free night for me

@davea
Ok, Thanks for the tip and for trying the menu out.. I'll try that tomorrow. I just shut everything down and I'm just about to make me some dinner and then it's netflix and chill for the rest of the night.

Just tried yet another menu, but I get the same result. "Bad arg letter" on the first line thats not commented out.
I'm getting more and more convinced that my printer is possessed by evil goblins.
Or maybe the display only understands mandarin and the only line in english it knows is Bad arg letter

@davea

Sure. here it is. Just rename from .g to .zip
0_1553533540149_DUET3D_12864LCD_MenuFiles.g

I just re checked my current menu files and they are not from dc42, but from jottesman.
Sorry for the mix up. The uploaded 'main' is from the jottesman menu.