pull the inspection cover/starter, and try for movenent towards and away form trans. then rotate the flywheel to load it the other way and try again. If you get endplay like the TC wasn't bolted on yet, you got issues.
I have had a couple broken flexplates, and its never kept the car from running(loud though) but If you have a crak sensor trying to read off it, I imagine it would flip its lid.