Seat ibiza starter motor keeps breaking?

i have changed my starter motor 3 times in the last year it keeps making a grinding noise when i turn the engine on|||The teeth on the flywheel are worn beyond service. Three starter replacements means you need a new flywheel and a new starter.|||make sure no teeth have broken off the flywheel and that the starter is disengaging after the motor starts.|||if your flywheels is all screwed up its gona mesh the gears together on the starter causing it to grind....i believe they can machine flywheels tho