The problem is the cover does not fit snuggly over the coil.
The cover fits tightly around the outside of the coil, but does not grip the inner part of the coil sufficiently to prevent the cover from bulging out in the center by around 3/16", allowing wet sand or soil to fill up the gap. This is a definite design fault, and I have had to use a small cable tie to keep the cover close to the coil. It seems Garrett have not addressed the problem, according to my supplier.

