Alrighty..

Firstly a systematic approach needs to be done to eliminate a couple of things.  Unplug power (from the wall) and remove.
Remove all 6 balls (before or after) and lift playfield to its upright position.

As Blair and Andrew have suggested, a check of the switch in shed would be my first area to look at.  If no issues identified then....

There is a note in Clay's guide about the loom rubbing against the upper right flipper coil stop.  I would carefully inspect this area to ensure the loom isn't shorting.

I would also do a visual inspection of the diodes on the coils to ensure none have broken.

See how you go.  We'll get it sorted.