The manual gives you a fair idea here. Reference for the Yamaha manual is THE6006 - I don't know if Philips is the same. Cause is either overload or overcurrent. The manual suggests that you can tweak the trimmers on the driver board but these are usually set correctly at the factory. I would guess that if this has just started happening and there has been no major installations at your facility that correspond with the error then leave the trimmers untweaked. Generally speaking you have three areas. 1. the motor is on the way out. 2. The motor driver board is nmg. 3.You have a problem with the cabling. I presume that you have checked for any physical impediment to the x-axis. Swapping the driver board with another machine takes about ten minutes and is where I would start. We still run three varieties of these machines (circa 1992), everyday and have never had a cabling issue. Driver boards and motors however have died. The older 21 Series machines would give you hell in the harness but in the Hyper series that would be unusual. Your local electric motor shop will often be able to repair a motor if the encoder is not damaged but there is no guarantee. I have also heard of a large plastic injection moulding machine in close proximity to a YM66 creating this error. This may be unlikely in your case. Good Luck. Let us know how you go.