make sure that the red wire is closer to the thermistor?? lost in translation? I respected the polarity of the other fan which has a keyed connector and cannot be reversed.
with belt holder oriented as shown the Y-end stop is not triggered. The switch bump falls right into the screw recess.reverse switch and problem solved
from step 4
Y-motor-mount should be somewhere in the middle of the threaded rod. The precise position doesn't matter at this time.
i did not see any precise positioning of the motor mount yet. It is kind of late to position it now. Or did i missed it?