Found it last night after having the DW try and wear out the slide switch and linear actuator from moving the slide back and forth and using just about every lubricant I had on the shelf. It was something in the linear actuator, and the only thing that worked to stop the noise was good old Fluid Film (IMO one of the best lubricants ever made and I use it on all my tractor stuff where there needs to be a film of lube) took several tries and wiping it down after I had it soaked and dripping while the DW moved the slide but after about 1/2 hour it finally stopped squealing.
John & Deb
2011 F250 Lariat FX4 Crew Cab 6.2
2011 Flagstaff V-Lite 30WRLS
Days Camped 2013: 16 2014: 5 2015: 3