Replace the microswitch, check the latch for the coil assembly, and the locking edge of the target.
Either the microswitch is out of alignment or contacts are used up, the coil latch is broken or bent, or the target needs replaced.
The "pulsing sound" is the game trying to reset the target and "get it up".

Check mechanicals, before electronics.
If it works reliably test mode, it is not a transistor unless you have solder point issues.

If you are extremely concerned about breakage, the best method is to use a hex post extender on those plastics and install a set above and below. The extra space distance will allow the extra protection properly. Otherwise install them underneath. The extra thickness absorbs the blow and will prevent breakage, but can spiderweb the ink screening. Installing them on top does not increase the protection significantly.

You "sandwich" a clear protector above the plastic using this extender for spacing. It screws into the existing hex post.

PPS-02-4935-1_(resized).jpg

We are only really talking about one plastic protector when the ball drops off the Battlefield, not the whole entire game.
Stencil template the protector, and cut it out with a dremel using 1/4" clear acrylic or PETG.
Now you have two protectors, one above and one below, "bulletproof".

If you like "The Shadow" listen to go the Radio Show from the 1950s. Makes the Alec Baldwin movie even more embarassing. Available via free podcast for listening while you work or drive.

The nostalgic force factor is high with you as a pinball padalwan. Some of the best quality manufactured items ever made were produced over 50 years ago.