@StephenRC:
When that G1 Y260 F3000 move occurs, the printer is already at X0 Y0 due to the G1 X0 Y0 F5000 in pause.g. After the moves in cancel.g are acted on, the dwc & paneldue shows X10 Y260. None of the axes positions are outside the defined printer area of 300x270x200, before, during and after.
The G91 has a G90 in the two macros and they only surround the z moves.
The print files that slic3r makes, have a M83 & G90 at the beginning.
Copied the cancel.g file over to the corexy with the DuetWifi. It worked fine, then changed the Y260 to Y300 for the max y on that printer, and it still worked fine.
Updated Duet085 to 1.17b, problem still there. There must be something odd going on with my Duet085. It doesn't always show the M117 on the PanelDue and every so often on power up the ethernet is unresponsive. Since the problem stops by using Y240, I'm not going to worry about it.