One of the cures has been to wrap string and the like around the male thread but it shoots loose quite readily. The most recent one I did I peened the threads back toward their original shape. and that tightened it up. The owner did not plan to fire the rifle but bought it for a collection. I told him it would loosen again if he shot it much.
I Locktited another years ago and that tightened it up and it shot ok after but that rifle was retired to a wall hanger after the owner died. I don't know what a permanent fix might be. The problem is the threads are very small and not made to last under heavy use, apparently.
If you peen the threads back and locktite it, it may become serviceable once again but the value of it will be destroyed. Likely if it's that loose, it's a shooter anyway.
There may be folks who specialize in doing a proper repair, I don't know.
Pete