Dual Extrusion First Layer bad

[njotha 0]

Hi,

Looks like I had messed up some settings:

Printing something with two colors (UM3) was no problem - until the day before yesterday.

Imagine: Head 1 white filament, head 2 blue filament. Printing a white square, 5 mm thick, a blue triangel in its center, 2 mm thick. The layout (in Tinkercad) is perfect. Las week it has been printed perfectly -- front a white square with an embedded blue triangel, back all white. 

Now (and I don't know why) the first layer is being printed completely by head 1 -- although it's printing the triangel seperately as if it would have liked to print it with head 2. Layer 2 and the following ones are being printed correctly white and blue.

 

Any help visible at the horizon?

 

Thanks a lot for any help.

 

-njotha