The older Kenmores with metal handle didn't seem to have this problem, but the ones with the gas pump handle seem to. Both of my mom's Whispertone canister had issues with the PN turning on and off, and I found that the plug in the handle has a plastic tab that holds it down, and when it breaks the plug moves up and down when you push and pull the PN to and fro, which causes the loose connection. Neither of hers melted but what I did to fix the issue was to glue the plug down where it should be with superglue.