First rule of flipper repair - check the EOS.

The EOS (end of stroke) switch should (must!) activate when the flipper is fully extended to prevent the coil burning out (although the fuse would normally blow first) - the EOS turns off the current to the main winding and activates the secondary winding instead.

It is quite common for flipper problems to be caused by incorrectly adjusted EOS (over time they can go out of alignment).