If it were me I would change all external bearings. Check bridge rollers real well and replace if needed. I hear they have an update kit for the rollers that does away with the bearings. I service mine regularly and have no issues with them. Also R and R all the oil in the gearboxes especially the bridge gearbox. it gets worked the hardest. I would take a close look @ the trolley/arch electric drive motor wiring harnesses that are routed through the E track. My M5's are 5 years old and the harness casings started to deteriorate last year and caused trolley issues. Change the 1"x1" female straight swivel @ top of trolley to boom. There is an update kit to change the boom set up over to a mosmatic 90 deg. swivel. But again I service mine a lot and have really good luck with the original set up. Look at the festoon rollers for bad bearings/corrosion. All these will definitely be easier to do on the bench/ground rather than after install.
