Summerwind, the plug-it cords can be very hard to twist a full 1/4 turn to make the correct connection when they are new. Your comment "twisted on as tightly as humanly possible" doesn't mean you it was on correctly. Your ability to twist the cord may be much different than mine. Your comments about your plug-it cords staying on your tools also makes me believe that you may have never attached the plug-it cord correctly when the tool and cord were new when the cord is at it's most difficult time to install. It may have come lose at some point as well. I'm not saying your at fault necessarily, some plug-it cords can be so hard to turn you truly believe it won't go any farther without breaking. They will turn the full 1/4 to lock correctly but it can be hard to do.
This isn't a problem Festool is trying to sweep under the rug. The manual clearly states the plug-it cord must be twisted a full quarter turn to be properly connected. Be sure to read your manual folks there is some good info in there.