My T17 movement watch stops running after a minute

Hi! Looking for some watchmaking opinions since I'm afraid I messed it up. 🤦

I just received a watch with a T17 movement. It was running fine until I decided to demagnetize it. I have one of these cheap demagnetizers and whenever I buy a vintage watch I do a pass or two just to make sure that the watch is not magnetized. It was fully wound before I did the pass. Immediately the watch stopped working. If I shake it very gently it starts running again very fast for like a full minute rotation and then the seconds hand stops again at around the same position as before. Shaking gently will repeat the process. I'll take it to a watchmaker when I get a chance to find what's wrong but until then it's gonna bug me.

Do you think this somehow broke something irreversibly in the movement? Thank you for your comments 😀

Thank you! After a few multiple passes trying your suggested way to de-magnetize the watch finally did the trick. Now it's running normally again. I never had a watch stopping before when using the de-magnetizer so I kinda freaked out that I broke something. Thanks again 😀