Not sure what to make of this, but my first layer seems to be using the wrong retract value. My start code finishes priming the second nozzle, and then returns to M135 T0.
That is fine if the first later uses Tool0, since S3D will retract T0, move the tool over, then Restart T0. The problem seems that if my first layer uses Tool1, my start code still finishes with M135 T0 (I don't want to adjust start.gcode everytime depending on the model...), the first command S3D applies is a retract of Tool 1 before it actually switches to Tool 1. The logic isn't correct. The first line of S3D code should be to select the Tool M135 T0/T1 before doing any retract or restart!
