The handle of the storm door has gone"limp" - but I can't seem to remove it from the door (even after removing all the screws). Is there something "special" about removing a Papaiz 323 traditional mortise door lock from a screen door?

I hate to purchase a replacement handle/lock for $70 if this is something like a spring that can be replaced. But I can't get the entire lock off the door in order to see what the actual problem is.