Tachihara 4x5 lock problem

Hello, folks. I'm hoping to find one or more experts on this camera here, after getting some help--but not quite what I need--over on Large Format Info. I'm in the U.S.
I’ve been having trouble with the front standard locks staying locked on my recently acquired Tachiara 4x5 (nickel-plated with brass "toggle" cam locks), especially one side. I tried replacing the old, somewhat beat-up brass shims/washers that sit topside between the bed and the cam, with new steel ones in three thicknesses: 0.1, 0.2, 0.3 mm. They slip. Subsequently, I tried to get nylon ones, after reading that Tachihara had begun supplying its cameras with these as early as 1998 (1998 post on LFI). Compressible makes sense to me. The only ones I have found in the right diameters (from McMasters-Carr), however, are too thick – 0.5 mm, according to the description – though I tried them anyway. The extra thickness doesn’t even allow clearance for the locks to be screwed in.
I have considered trying to sand (somehow) the steel shims with some superfine sandpaper (the gray stuff, maybe 400 grit?) to give the upper surface some friction potential, but I’m no expert in fine mechanisms and metals, and I’d rather get proper guidance from someone who knows.
The back locks, also with the new steel shims, hold fine. (In fact, the ones that came with on camera were too thick to allow free rear swing, which is now fine with the new ones. Some other adjustment is needed to remove a little vertical play from the rear standard, but that has to do with the large black plates that jut out.)
Therefore, I am seeking either/both a source for thinner nylon washers and/or some expertise from someone with experience with this camera, preferably with this particular problem, who can help me get it operating properly. It’s frustrating to have gotten the camera and not be able to use it! The one, better side might stay if the other did, but it's not completely solid either.

This is a resolution to this just-started thread, some hours of further experimenting later.

No one ever accused me of mechanical genius, so this is only a bit embarrassing. I discovered that the problem lies not in the shims but in the screw holding the cam to the pin, namely, the screw needed tightening. For those who know the mechanism, enough said. For anyone else who may be interested, the following brief explanation, as well as I can elaborate.

The cam is made as a sort of yoke that fits over the tightening pin; the two are held together by a very small screw that passes from outside one side of the yoke, through the center pin, and through the other side of the yoke. Picture an upside-down, 3-dimensional U pulled down like a hat over a 3-D I (it's sides are flat), with a screw passing horizontally through all three to hold them together. As the screw is tightened into the far side of the cam yoke, the two sides of the yoke are pulled together, creating friction with the sides of the pin. If the friction is just right, the cam, which has a pole coming out of the top that looks like a toggle switch, can still be moved but is held more firmly in place as the cam is rotated to make pressure against camera rail in the bed.

As I said, these are small screws, and in my concern not to over-tighten them, I was leaving them too loose, and they lacked the friction to "lock."

Live and learn. If anyone knows who might source these (presumably Japanese) screws, please let me know. I'd like to have a few extras on hand for the long run.

They're likely Metric. Some hobby shops carry them for RC cars or planes. McMaster-Carr probably has something
but you're going to need the size. A machine shop may be able to measure them for you