92 Ford Explorer

Where is it cracking?
Here are some things that run through my mind when I hear you keep braking flexplates:

Transmission and engine improperly aligned. Maybe a shim or a washer stuck between the two on one side, or the transmission shifted either too far side to side or up and down.
High transmission line pressure, causing the torque converter to be pushed overly hard against the flexplate.
Improperly torqued flexplate bolts.

I hope this helps. Flexplates do crack, though not often. They tend to fail with age, and mostly crack around the flexplate to crankshaft bolts.