Dual extrusion problem with 4.9

[RonaldKeller 0]

The first used core on my S3 prints fine but the second one does not extrude any material.

Switching back to 4.8 solves the problem.

[nallath 1,123]

Yeah, we messed up there. Even though we test dual extrusion models for every release, the model that we used to test it didn't show the issue. We've fixed the issue for 4.9.1 and have updated our test procedure so we will catch it next time.

I expect that 4.9.1 will be released this week.