If the magnet does work sometimes it isn’t bad.

The magnet gets its power from the fliptronic board. Good place to start.

Is the magnet controlled by its own flipper type button or by something else

The magnet is controlled by the cpu board via a ribbon cable to the fliptronic II board. Since this problem is data related, the ribbon cable is suspect. With the machine off unplug the ribbon cable and reseat it to help clean its connections. All it takes is 1 wire bad or bad connection to keep the magnet from working.

Rollovers are part of the switch matrix that get connected to the cpu. The fliptronic board still might data processing problems.