After a duplicate print job completes and the print heads try to “return home” the printer heads push up against each other. Its as though the left head it tying return home to the right side and the right printer head is trying to return home to the left side. This makes a griding sound in the gears.
Hi gmarkusic,
it took quite a while… Your observation is highly likely the result of a firmware bug that occurs when the end of the G-code file on the SD card is reached. All remaining instructions in the queue get processed in dual mode with the left extruder. The bug applies to all modes except single mode. In your case the collision happened when the left print head tried to move to the right parking position instead of the right head.
I fixed this bug in my current firmware version that is available here.