The plastic shaft separates from the metal plunger and ends up in the habitrail. First one was an older style where a pin connects the male plastic piece to the female metal weighted piece and it broke at where the hole was drilled horizontally through both parts. Newer ones are just press fit. Replaced with press fit and I believe it has happened twice, each time replacing with new and taking the old and JB slow epoxying it for emergency use. Tomorrow the epoxied one goes in as apparently press fit just ain't good enough. This time I will check grommet where the weight seats or any other obvious things I may have overlooked that is stressing this out. Any other thoughts from someone who may have encountered this problem? "I'll be back..."

Thanks eyeamred2u, to be clear, this is not the ball cup, nor the pin that holds it into the back plastic shaft. It is the shaft itself that separates from the metal plunger that fits into the coil sleeve. What ends up in the habitrail is the cup, pin and black plastic rod that sits on top and into the metal plunger. Nothing theoretically is broken. Just separated. Take a look at this: #515-9835-00 the pin keeps the plastic together with the metal part. Here is the correct part, and trust me after 2 beers of time looking, it' ai't easy to find. Notice the metal and plastic have no connecting pin. #A-11336 Now that said under search, THE WRONG PART COMES UP ON MARCO. It's not a compression ring.
https://www.marcospecialties.com/pinball-parts/A-11336
Notice no pin.
And that is the part we got from Marco.

Thank you! And yes you solved my problem! But not necessarily in a good way, at least from a time consuming perspective. From Action Pinball:
INSTALLATION NOTE: This is an aftermarket replacement part that requires drilling-out the retaining pin hole in the tip of the plunger to 3/32-inch diameter before inserting the retaining pin.
Imagine if you bought spark plugs and there were no threads on it. Aftermarket. Tap your own.