I have an e3dv6 with the latest heater block and thermistor cartridge. I had an issue where the temperature would just start fluctuating a lot and sometimes causing a thermal shutdown. It took me some time, but I found out it's because the thermistor cartridge had come loose. Last week I tightened it back down following the instructions, just getting the grub screw to touch then 1/8 more turn of the hex wrench. Now after just a week or so of prints, it's starting to come loose again. I don't want to overtighten it like the instructions warn against, but how can I keep this thing from coming loose all the time?