Hi, folks. This is a follow-on to some earlier posts. I’ve been having trouble with the front standard locks staying locked on a 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 Tachiara had begun supplying its cameras with these as early as 1998 (1998 post on this forum). 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.
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!

Thanks.