How can I remove K beater from my Kenwood patissier which is jammed

Only a bit of CRC and some brute force is going to work. Unplug the machine. Remove the bowl, lock the head down, squirt some CRC around the top of the paddle where the shaft goes in. Get someone to hold the mixer from moving about then grip the paddle firmly with 2 hands and turn it left and right. Gradually you will begin to get increasing movement until in the end you will be able to unlock it from the shaft. Once it is off you will need to thoroughly clean the shaft then you will need to scrape out the inside of the hole in the paddle. I carefully use a small round file, I am trying to clean the hole out, not increase the size of it beyond what originally was. The hole size has become smaller over time because of flour or similar entering around the shaft during use.