[Mark Yacavone]

Very rare, but entirely possible.
Does it have an anti ballooning plate? I ' ve seen leaks under them, where it took a while to get out to the outside.
You could rig up a cap and plug deal and run about 30 psi regulated air into it, and then check it with soapy water spray.
Any local rebuilder could make a welding pass around the hub with out disturbing anything else as long as the hub is still concentric.
You would want to drill an 1/8" hole at the outside edge near to the main weld seam.
Stand it up on it's side for a few days, then flush it out with safety kleen or mineral spirits, then blow it out good.Just mig up the hole when you're done.