Well your volos WOULD crack if it was the 'A' batch of volos, which incidentally can be changed for the 'b' batch that does NOT crack, you can check this by looking at the sole of the volo and the production stamp would show either an A or B.
I dived with various people with various types of fins, including quattros. I find that although I have to kick more, I move much faster and the load is much lighter on the legs and knees. I had to change my kicking style from my use of the Plana avantis but it was a mere minor adjustment, requiring 2 dives to find the optimum kicking style. Incidentally, I been able to flutter, frog and back pedal using these fins.
If you still have your broken volos, have them changed out, and resell them. Remember, get the B batch.