Can't Desoutter MIM Tele Pickups

Hello, I am new at changing my own guitar pickups and am trying to put in Twisted Tele pickups. The guitar is MIM, and I ran into a problem with the wiring. I cannot de-sauter any of the grounds. It is almost as if they are permanently welded in place instead of being sautered. I have changed my Strat pickups before and it went perfectly fine, I was able to desauter it easily, but this guitar seems different. I was wondering if you have run into this issue before? Do you have any advice or videos you can link me to? I can also give an email for easier communication if needed! Let me know if you require more info too! Thank you so much.

PS: I have tried turning the heat up very high, and I am using a sautering iron.