Which machine?

replace the balls? Make sure they are carbon steel.

Ok. Odd I have a SM as well and mine hasn't had a magnetized issues since I've had it. It's been almost 2 years.

And the problem went back again pretty fast.

Your wording indicates that the problem was fixed temporarily, then returned? If that's the case, then you are still using the wrong balls.

I would guess you probably have a divot in the trough causing the hang-up, and not magnetized balls (although that could be the issue, especially if you bought balls that easily magnetize)

Get in there and look for some very small divots where the ball travels in the trough. A quick pass with a dremel will take care of any divots you may find.