Hi there !
After many years having trouble with my LukeII for tuning stability (I had this problem from the beginning), I recently solved the problem.
Problem : As many people has described, using vibrato bar lead to abnormal (too much) tuning issues.
The guitar was expertized by Luthiers, nut was changed and lubed etc...
Whatever I could do, when I was dropping the bar, the guitar was suddenly totally out of tune.
(It is not whammy bar madness here. To me, dropping once the bar is a standard test to check if the guitar stays in tune after the strings are broken up).
Solution : I took the bridge out of the guitar and examined it.
The knifeedges were worn.
As I was fed up with the problem and because all the experts just failed solving it I just decided to try solving it myself :
I took a small and round file
I slightly filed the inside of the knifeedge until I got an even surface showing no more worn parts and and get back the round edges. I filed with an angle (or "slant" way) to keep the edges sharp.
... And it worked !
There's absolutly no doubt it solved the problem. The guitar keeps tuning very well now.
I would not recommend doing it yourself unless if you first made checked the guitar by an expert Luthier (the nut, machine heads...) Any way if you have this problem and if you're fed with it, you can take the bridge out of the guitar to examine it !
Hope this helps people who still have trouble keeping their guitar in tune !

After many years having trouble with my LukeII for tuning stability (I had this problem from the beginning), I recently solved the problem.
Problem : As many people has described, using vibrato bar lead to abnormal (too much) tuning issues.
The guitar was expertized by Luthiers, nut was changed and lubed etc...
Whatever I could do, when I was dropping the bar, the guitar was suddenly totally out of tune.
(It is not whammy bar madness here. To me, dropping once the bar is a standard test to check if the guitar stays in tune after the strings are broken up).
Solution : I took the bridge out of the guitar and examined it.
The knifeedges were worn.
As I was fed up with the problem and because all the experts just failed solving it I just decided to try solving it myself :
I took a small and round file
I slightly filed the inside of the knifeedge until I got an even surface showing no more worn parts and and get back the round edges. I filed with an angle (or "slant" way) to keep the edges sharp.
... And it worked !
There's absolutly no doubt it solved the problem. The guitar keeps tuning very well now.
I would not recommend doing it yourself unless if you first made checked the guitar by an expert Luthier (the nut, machine heads...) Any way if you have this problem and if you're fed with it, you can take the bridge out of the guitar to examine it !
Hope this helps people who still have trouble keeping their guitar in tune !