maybe fixable if you can get the tank out of the asa, then have a look at the threads on the asa and see how much damage has been done. If there are loads of metal fillings and the threads look worn down probably time for a new one!
Ide say get a new one as if there is damage to the threads it would indicate the threads are now weak (hence the problem in the first place), plus you can't really go wrong with getting new