I had a spy up until last summer. Pop bumpers activating without hitting the switch is usually caused by the switch blades being set too close, any vibration from the pf near the pop bumper may set it off. Occasionally, but rare, the pops activate from an electrical field in the game, known as phantom activation.

Typically a bad coil on the pf will blow the 1 amp fuse under the pf before blowing F4. I had a Meteor that was blowing f4 and it turned out to be dirty EOS switches and not the coils. Since Spy has 4 flippers, I would look into that. The pop bumper thing may just be coincidental. If EOS's look good, check the resistance of the pop bumper coil, should be around 10.5 ohms. See if the coil is getting hot after a few games. Make sure the pop ring is moving freely, not binding. A swelled coil or dirty coil sleeve will add resistance to the movement of the plunger. Check coil diode. See if the driver transistor is getting too hot. There should be a chart in the game to ID the transistor number, if not, it's in the manual.