It's probably max contacts. The game has an option which lists how many things can be touching each other at the same time, if the maximum is reached, you won't be able to dq.
Changing maxcontacts to a higher number, like 16 or something, will make the chance of this happening alot smaller.
You won't get a refund on this, I know that from experience.
Next time it happens try to push yourself away from your opponent and ungrab.