Dual Extruder: Struggling with stringing on right module

I have a problem with lots of stringing on the right nozzle.

I’ve done a bunch of calibration to find good temp and retraction settings. Print results are good on the right nozzle when the left nozzle isn’t used. However, when running a dual mode print I always get a huge number of super thin strings from the right nozzle. This happens with both Luban and Cura with several different filaments.

I’m starting to think there is a firmware bug that stops retraction in this mode or something like that. But I haven’t seen a lot of reports of this, so a bug seems unlikely. Has anyone else faced this and found a solution?

No seams to be working with others. So i highly doubt firmware.

What slicer are you using?

I’ve seen this with both Cura and Luban.

now retraction by default is way off.

im 1mm@35mm/sec
and 5mm @20mm/sec on nozzle switch.

Seams to work well might give you a starting point.