I recently replaced my washer, bolt and nut on my 1967 kit.

Maybe a 2'nd washer would help?!?

Maybe the knurling is just too worn down on the L-arm. Can you get stuff re-knurled? Seems unlikely....maybe a replacement L-arm.

Or a bit of tape on there....hmm I don't like that idea. Is it loose on the tom mount or the rail mount?

I wonder if the L arm is not a Ludwig part? A oddball non Ludwig part(s) of some kind or possibly a MIJ that was added at some point? Mitch has a very good point on the knurling being worn down. You can wrap a small piece of tin can cut to size short term. Cut it with sizzors and wrap around just be careful as it's razor sharp. But it'll take up the excess play between the arm and receiver for the meantime. If you can post some pictures of it the guys here are pretty sharp and might spot something your overlooking. But it sure sounds like worn out or incorrect parts. If it's not holding on the tom mount side the eye bolt insert maybe shot if the knurling is not worn. New replacements are sold by Ludwig but seem to be out of stock at the places I shop at right now.

I'm assuming the top part that holds the L arm is the "telephone dial" type? Those don't hold well. You could look for a late 60's version with the gear teeth...they hold much better. That would also be like the reproduction version that Steve Maxwell sells. I have a late 60's gear teeth holder on my '58 Ludwig and it works great!

If it is sliding on the tom mount side...then I would look for a little newer tom mount. Very early 60's versions have a screw that just butt up against the L arm shaft, while later ones use an eye bolt inside with a wing nut and hold much better. Hope this info makes sense and is helpful.

The "telephone dial" or "clock face" consolettes were Walburg & Auge I think. The later ones were ludwig manufactured. I bought a steve maxwell repro L arm and it works well but the finish isn't as nice, its Chinese made. It is a wear part so replacement may be nessisary, for the sake of playability.