The problem is as Chris stated, that the standard bolts have side clearance and rely on the bolt stretch to clamp the flywheel to the crank. The clamp friction between the crank and flywheel provides the drive.

In a competition engine rotational loads are a higher order than standard engines, load direction is constantly reversed (especially during down shifting or during incorrect gear selection -buzzing).
The standard flywheel bolt clamping force can not provide sufficient friction between crank and flywheel in this circumstance, so the flywheel starts to move. The bolts limit travel movement while they are being bent around the holes in the crank. The problem gets progressively worse until the flywheel is moving so much the bolts can no longer take the side loadings on them. Eventually they fail through a combination of shear and bending forces.

To fix the problem first clean the flywheel mounting face ensuring it is flat. Re-thread the crank bolt holes to fit larger ARP flywheel bolts. Thoroughly clean the holes and blow any particles out. Larger bolts increase the clamp load and also the friction required to make the crank move.

Secondly, fit three X 4mm diameter dowels at 120 degree intervals to totally remove shear loads from the bolts and who's shear force is added to the clamp force before any flywheel movement can take place.

Zero balance the crank, crank pulley, flywheel and pressure plate individually. Then balance the components as an assembly and you will not have a problem.

I always clean all components with parts cleaner wash then thinners in a spray gun.. Parts are then placed in a metho bath till removal and air dried with a compresssed air nozzle. This primes the part for best quality bonding of loctite

Use 601 loctite on the bolt threads and no lube. Torque to bolt makers specifications in one step.