Are you sure they're magnetizing and not just getting stuck? I've had success using a flap wheel to sand both sides with a dremel.

Does a piece of steel stick to it? Nail, bobby pin, needle, something like that?

I recalled from years ago that heat can be used to remove magnetism from magnets. I wonder if the same concept would work with a metal pinball part that's been magnetized. Ie I wonder if you could put the part in the oven for a while and let it bake and then it's magnetism would be gone?

Oh yeah, I meant you would need to drill it and rivet it. Just the metal parts

soldering gun is a poormans degausing ring

Actually its a lot easier.

Remove them and hit them with a hammer a few times. Done

The blow from the hammer actually reorients the dipoles to randmoize them and the magnetism goes away.

Would do this all the time in the field on Ms. Pac Man video monitors. People thought I was crazy until the ugly green corners became normal colors again.

Take soldering gun and hold sideways, body up to the glass over the screen. Turn on (So, plugged in with extension cord or in the service outlet of the pin next to the game) and rotate in small, circular motions around the outside edge of the monitor. About three cycles of this fixes all what ails the monitor.

You can take the coil stops and throw them hard onto a concrete surface with some results as well. Usually, the parts disappears though and you end up replacing it with a new, unmagnetized part.

You need one of these.....I use them for tape machine heads, but have used it to degause and demag other things.

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I still have one similar to that from Olson Electronics. Akron, Ohio.......

Hahaha- absolutely

Put them in the freezer for a couple of days.
Also, be sure the brass insulating washer is installed between the coil and the frame.

Put them in a brown paper bag, take them outside on a sunny day. Hold the bag over your head and run around in the street clucking like a chicken.

Done and done!

soldering gun puts out a changing mag field, just bring it close to the object, passing up and down the object

Ah got ya. Yeah I can't imagine most people would have access to anything that hot.

Hot or cold works. In the freezer for a few days will do it. I don't think I've ever come across one that was magnetized though. They usually stick when the coil is not magnetically insulated from it's frame.

That's what the brass parts around the coil stop do. They break the magnetic path.

There's usually a brass washer between the coil's core and the frame. Later Gottlieb's had plastic molded around the end of the core so that a washer was not needed. I'm not sure how it's done on "Blue Chip". I owned one once, but sold it. As "homepin" states above, there's brass in the coil stops, and the coil stop itself has a nylon bushing and a nylon insert nut to keep it insulated. That's on coils with plungers such as steppers, pop bumpers, flippers, etc.

Again, there should probably be a brass washer between the core of the relay coil (hole where the screw goes in) and the relay frame. The screw that holds the coil in the frame should be brass as well.

I've removed hard drive magnets from their backing using a 650 heat gun to soften the glue. The magnet was significantly weaker when I was done. So the oven may indeed work. It's free to try.

A propane torch would surely be hot enough, but I think something else is the issue here.

Just to clear up what may be a confusion point here...

The soldering gun method being talked about here (move in corcular motions close to the magnetized element) has nothing whatsoever to do with the temp of the element. It works because the soldering gun is plugged into an AC voltage and the tip basically forms an electromagnetic field that oscillates and scrambles the aligned field in the metal.

Dont try to heat you pieces with the element- its not hot enough to do anything by heat transfer- but you will very efficiently melt all the plastics near it.

Check some of the other relays that aren't sticking to see if they have a brass screw and a brass washer. The washer does not go under the screw head, but it goes between the end of the coil where the screw goes in, and the steel relay frame.

You can see this coil has a copper piece on the end of the steel pole piece. This is acting to break the magnetic field in this particular design.

There are many variations and methods of doing this.
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Any chance you are confusing a lock-on or a weak lock-on for a magnetized armature? When it is "stuck" on, does turning the game off release it? Or can you get it "stuck" with the power off?

I had that happen only one time, I think I just put one or two snips of electrical tape on the coil side of the armature, but it wasn't one of those 'always on' coils like a hold relay that get hotter than hell or it would probably end up melting it. I always look for the easy way... if it works.

I had a similar issue once. I took the plate and sanded it smooth to be sure there was no mechanical binding. Then beat it with a hammer for a while. Then used a torch and heated it a couple times. After that my problem went away

I wouldn't recommend the tape technique. I tried this on a Grand Prix I had on location (so it got a lot of play). At first the tape fixed the issue, but eventually the tape molded to the shape of the coil head and actually made the sticking worse.