It's unlikely the crane is the issue, though the latch may be. Here's a good drawing and a source for some parts, though they are sold out of cranes.
When you say "loose", do you mean fore and aft, left and right, lock-up? it locks up at the front and the rear, so either or both may be a problem.
Parts 19,20,21 for the rear lock up, parts 24,25 for the front.http://www.gunpartscorp.com/catalog/Products.aspx?catid=1976