you said "air tested" deeper but "in ground" hunt didn't appear to do nearly as well as the other metal probe - Pro Pointer
The reason is very simple. I call it is medium Detection parameters
Parameters are different from Soil - water - sand - stone
when the probe be automatic adjusted sensitivity it should follow with target medium, so "air tested" the medium is Air
but the gold and metal are underground when you put into mud - the medium changed and you should adjust sensitivity immediately
this is simple tech solution you have to manual adjustment every time when you detecting different medium air or water or mud
The qualified metal probe is
1 . TMP-A(on land) TMP-B ( underwater)
2. Pro Uni probe (on land)
3. Sun Ray X-1 (on land / underwater)
4. Bullsyes II (on land)
above Four models can adjust sensitivity to meet the different medium
and 1. 2. models the probe end 0.55 inches, this is the key to find smallest gold grain and only TMP is pocket probe 7 inch length
Minelab design Length is 9.3 ( 237mm )
is the same as Metal Probe MD2012
Coincidence
They may be known short length will cause faulty alarm