You mean a soft fork.

A hard fork should not cause that.  It should only make invalid transactions valid, not the other way around.

However, a hard fork could enable a new type of "lock breaking" transaction that allows the locked coins to be spent before the expiration date.  That would invalidate the refund transaction, which would be rejected as a double spend.

I don't know whether such a change would still qualify as a hard fork, though.