First post : pop bumper fires when spinner hit

Hang in there Can you tell us if this problem occurs when all drop targets are reset in the up position or only when some drop targets are knocked down (and which ones)? It will help to build a picture of what's going on.

Let us know the result of the switch test when you've done it.

Was this machine working before or have you just bought it with this problem (just wondering if it's a new issue or pre-existing)?

Looking at the switch matrix schematic, your symptoms are pointing to a stuck coin chute 2 switch (switch for the center coin slot) and if it has a diode (there may or may not be a diode there), the diode is probably shorted.
So can you have a look at this switch and see if the wire actuator is in the down position - compare it to the other coin chute switches for reference. If there is a diode on this switch, can you check it?

The switch test in service mode will tell you straight away if this switch is stuck, so recommend you run it. Just press the test switch inside the coin door 5 times to get to the switch test.