Steve, was your printer working correctly to start off with and has now developed this fault?

If it developed it, it is probably a failing stepper motor cable - usually the one that goes to the motor mounted on the slide rails to the right hand side. When these start to fail due to the repeated bending, they produce interference that stops the printer and often causes it to reset.

They are difficult to test until they actually stop working altogether, so often it's better to just replace it. Simple DIY job to splice in a new length or if your soldering skills are not great, you can buy one ready made. - https://www.flashforge-eu.com/parts-...orPro,%20Motor