Extruder motor is not spinning on tool # error occurs often  

Extruder motor is not spinning on tool # error occurs often

I repeatedly get the error "Extruder motor is not spinning on tool #" with my XLIS 5 tool. At the exact same point in the print the printer will reliably have a catastrophic error and freeze, failing the print job. At first this would only happen on tool 4, but now it also happens on tool 2 with different print jobs. I have modified the print slightly and re-sliced it but the same error occurs. I changed the tool to tool 1 and the print worked flawlessly.

Looking up the error link sends you to this trouble shooting page, i tried the fix it suggested but nothing has changed. A comment in the page mentions cleaning the extruder cable plug contacts with isopropyl alcohol which I also tried, but it has not fixed it. 

The fact that this error is repeatable in the EXACT same place to me seems like it is impossible to be a faulty connection, it has to be firmware.

This error has happened on tool 4 with two separate print jobs in a row with different materials and models, and it has happened with tool 2 on three prints. I essentially can't use tool 4 or 2 at this point as i cant have prints randomly cancelling partway through when i print large, expensive parts.

I can upload the G-code somewhere to help diagnose this issue if required.

Has anyone else had this issue and have they managed to fix it?

Thanks.
-Tim.

(Re-posting here as it was in the 'XL (Single-Tool)' forum previously)