Boy, you sure a interesting scenario going on there!

What shape are your bushings that hold the front stabilizer, anti roll bar, to the frame of the car?

Are the bushings on the both ends of the end links that connect to the stabilizer in good shape.

If the flat ones on top are not nice and plump, they will make a squeaking sound that will come and go. They can drive you nuts without you having any loose washers up stairs! II(:-)

I lube all the rubbers with a silicone grease that will not soften rubber and is rather inert. It's used on "O" rings by plumbers.

If you had a loose cartridge body would it not be more like metallic clunk or thump? If the cartridge went totally flat of gas or oil charge that might explain a rattle inside itself. You know the valving mechanisms internally sloshing around. A sloshy and squishy sound of a shot shock absorber. Not a rattle?
It would not stay extended either but the cartridge housing should be locked in, top to bottom.

I cannot imagine the spring bopping around but the coil endings should be located in a pocket stop on the lower half of the strut. Unless the orientation if off just enough to make it set crooked. Still, I think it would make a popping sound like a cracked spring?

A rattle to me is more of a tinny sound. Like a loose dust shield behind the brakes? Could there be a crack in one. Very Rare indeed. Exhaust heat shield could work?

I think I painted enough oddities with my armchair imagination. I am really curious though to what you will find.
Good luck and happy hunting!

Phil

That's the one. I have quieted a rattle down by adding additional washers.

I would make sure the gland nut is tight as well.

Dan