Considering that there is a crystalline structure that absorbs the signals coming from the scanner, I would have to agree that your idea makes some good sense.

For the scanners that can get through, and remain, however maybe that has to do something with it's ability to hone in on the certain properties of these crystals. Since every suit has these to some degree, then maybe the scanner is sensitive enough to pick up these signals but then again how do you figure out how long it will last in there?

What if the magnetic waves from the scanner act sort of like light does. Since light is both electric and magnetic, it passes through objects like Glass or Diamond. But when it passes through it will slow down depending on the material. This is determined by the refractive index of that material. For example, Light passes through glass, but is slowed down in it's new media of travel. Diamond can slow down the speed of light by about 2.43 it's normal speed.

Since the scanner's waves are more like magnetism in property, then it could be possible to assume that something about that causes it to stay around in the shields much longer than other objects. Maybe it tends to like the shields and future-tech armor with depositions of dense crystals on the surface. Possibly because these future materials have far more complex structures in the nano and pico range. 10^-9 meters - 10^-12 meters

So the density of the material may cause the magnetic waves in the scanner to stay in the particles of the dropsuit much longer.

And what of dampeners?

Well, I'm no master physicist. But I do think that frequency determines the overall strength of the signal. If you could change the frequency of the oncoming scanner wave, to where it speeds up the process that the waves undergo as it travels through the atoms of the crystals, than maybe you could streamline it's pass through your suit to the point where the scanner cannot detect a change in the types of mediums that it's designed to pick up.

Which is maybe why the scanners say "No margin of error" when they don't pick up any enemy dropsuits. Because maybe the scanner calculates the changes in speed that the waves undergo as it passes through mediums like shield technology. Like an electromagnetic camouflage.

Or maybe it could just absorb ALL of it like the stealth fighter planes do today to radar signals, using materials like carbon nanotubes. These are very similar to diamonds in a lot of ways. In fact, carbon nanotubes would probably be the most viable way to make this type of armor while keeping the suit as light as possible. It's 100x stronger than steel, but only a third of it's weight.