OK, tomorrow evening I’m visiting a friend who knows much more about PCBs than me and who has lots of equipment, including a small reflow plate.
Could be, but as I explained above the Y-motor wasn’t even connected at that point.
It’s definitely broken and can’t easily be opened.
I see, yes, I had done that before sending the last M122 command.
Thanks for all your help, @jeffeb3. I’ll keep this thread updated with my findings.
Yesterday evening, I spent three hours with a friend of mine debugging the SKR Pro over some beers.
Turns out that two of the black female headers that the TMC 2209 driver plugs into, were somehow defective. From the back of the board, the solder connections looked okay, but my friend ran some tests with his equipment and found out that they weren’t conductive somehow.
We replaced the female headers, with some that he had laying around, and now it works like a charm.
I’m so happy that I don’t have to replace the entire controller board! Having to buy another Nema 17 is already bad enough.
That is great news! I am glad it was something relatively simple like that.
Are you completely sure the nema17 is busted? The motors are dead stupid and really don’t often fail. More likely, the wires going into/out of the motor are broken.
But those are at least somewhat “commodities” compared to the whole controller.
Since I’m unable to open it, because of the feeble, overly soft screws that are already nearly stripped and still won’t budge, it’s really hard to tell. I re-did the JST connecter, but the weird stutter-y behaviour persisted.
I already ordered a new one, and I don’t want to waste more time on the other one. Instead, today I redesigned and re-printed the truck clamps of the x-axis to accomdate a L-profile for cable management. 
