The soil hasn't changed.. he also determined it was not the coil. Appears 7 update may be the culprit.
After watching the video's I tend to believe his soil did not change but the the amount of water saturating the soil has changed. That moisture is affecting all of his other detectors now too. He states the clay in his area holds the water longer than sandy porous soils.
The wet mixture can dissolve minerals that are in the soil. The question might be what mineral are present and which ones affect the detector. We all know Salt is one mineral that causes issues.
I think he shows some tests that are pretty conclusive supporting his theory of saturated soil.
He was was also honest enough to admit he was wrong about blaming the Ver 7 for the issues.
I also think another confirming test would be if he traveled to another area with sandy non clay soils and performed the same test with his D2. If the Detector works properly there, then that would support his soil theory.
I have interest in his findings because I live in an area with heavy clays from an ancient lake bed and the Mineral content reads high at 72.
During the winter the soil can freeze as deep as 3 ft.
In the spring the top layers thaw first creating a bowl affect holding water in the clay. The froze ground below will not let the water drain. I have seen tractors and bulldozers sink and bottom out in the mud leaving tracks 18" deep.
I want to know more on how that affects the detectors depth in my area.