Not surprised you have tuning problems. The Kahler string clamp always sucked IMO (though the trems were great) - I had one on a Charvel & it did become unreliable after a while. If it was a guitar of little value, or something that I played a lot, I'd be tempted to get a Schaller locking nut (like you typically see on Floyds) fitted.
i was thinking of getting something done, maybe just a replacement clamp and a new nut, but i had thought of a floyd style nut. i'd just be a little afraid of major surgery.
Yeah, I guess I'd be a bit leery of any major change on such an unusual guitar - it only takes Dave Grohl to be seen with one & you'll have buyers queuing up to offer you a fortune :)
Basically, it's a flawed design because with the string going over the nut, unless it's aligned very precisely, the string has to be pushed down slightly to be held by the clamp. In other words, the string wants to lift to make a straight line from nut to machinehead & has to be forced to sit at the bottom of the clamp. With time the clamp just doesn't hold it tightly enough.
Then there's also the problem of the string grabbing slightly in the nut - even though there's only ¼-½" of string between the nut & clamp.
A Floyd nut solved this as the string tension holds it flush to the surface of the shelf, so the locks only serve to prevent lateral movement.
