I know that this comment will be greatly frowned upon but oh well here it goes anyway. If the problem is determined with the wood and not a warped plate, find a competent smith to scrape away some of the inner in-letting for the locks and bed them properly with one of the many compounds available, the smith should know what areas to relieve to allow the locks to function properly. If a good job is done no one will ever know without removing the locks and bedding compound is far more stable than wood. Of course it has worked this long with out an issue so bedding is probably overkill, however it should give years of service to the gun without a hitch.
