Let me start by saying that if I had not made the cover over the changer motor clear so that I can visually SEE the lock rotate I really do not know how I would have figured this one out. I have been printing just about all the multi-color objects I could find online. Super reliability! One try and I got a good print almost every time. Until I tried to print Tigger: https://www.thingiverse.com/thing:2807122 The TC got to right below the arms, but when I went out to the garage to check, two tools were lying on the bottom of the machine and the carriage was running tool-less. Ag! I cleaned it up (note the collar on one Nimble broke... more on that in another post) and tried again, but this time when the carriage went to pickup the tool the tool fell off. Watching the mark I made on the gear inside the carriage housing (I could see it because I printed the cover in translucent clear material) I could tell that the cam was NOT rotating. WTF!?!? Wow. What was going on? It took me awhile but eventually I found that when the accident happened (and I could never really figure out how it happened) when the changer went to the tool it was out of register and crashed into the tool. In the process the crash knocked the insert for the cam that is CA glued and pressure fit into the tool plate out of alignment. OK... I remove the screws holding the tool plate to the parking mount, the aluminum part holding the V6 and the downward fan duct allowing me to get the plate off of everything easily. Until the one screw that would not come out. I had to drill the head off of it to remove it. NEVER USE LOCKTITE WHERE YOU NEED TO SERVICE!!! The insert pops back in OK and all works OK now... but this happened to TWO tools not one!