A few days ago I encountered the same problem with my DDM60. I suspect that the problem is the data from the servo / encoder. meanwhile I plug the powered usb hub on my mounting and it looks like it can return to normal. ASA gave me 3 meter USB cable maybe this is too long so data from servo / encoder is lost. shortening the USB cable is quite possibly the right solution. Thanks and sorry my english.
Regards,
Ishaq Zunaedi