I rarely visit Pinside as I am based in the UK. But may I thank the guys on here for investigating this so thoroughly.

I have this phantom pop bumper issue on my Paragon. I get one pop bumper giving phantom firings. Always the same popper. No score is registered, no sound is produced. It seemed to happen every 30 seconds or so and is almost certainly triggered by the flippers. I think it may also be triggered by other solenoids firing on occasion too, but I can't be sure.

I also got phoney tilts that seemed to be triggered by solenoids firing ! Replacing the switch capacitor on the tilt bob helped reduce the frequency of the phoney tilts, but did not eliminate them

I then swapped out the original MPU and Solenoid boards and inserted new Altek units. This reduced the incidence of phoney pop bumper firings and eliminated the phoney tilts.

I then cleaned the flipper and eos switches with with very fine abrasive sheets and then isopropyl alcohol. This seemed to reduce the frequency of phoney pop bumper firings even further.

I will now work down the rather helpful summary of actions given by BJM-Maxx above !