Strange problem with A10M

[AlexanderMason]

Hi everyone. My A10M which has been working perfectly for many months has suddenly gone nuts. Every 5 or 6 layers the hot end will head to one side of the build plate (not always the same side), extruding filament while it's going, then go right back and start printing again. I end up with a bunch of loops of filament all around the outside of my print. Also, every now and again it will just stop and not move again. There's no error on the panel or bad noises, it just stops. I've tried different STL files, I've tried different memory cards. I've reset the EEPROM and loaded my stored settings. I've also tried reflashing Marlin (I've added a 3D Touch leveling sensor) and put back in my settings for steps/mm and z offset. I've also checked to make sure the cooling fan over the control board is running and all the connections are tight. None of this has helped. Any suggestions of things I should try next?