I am not surprised.In Colorado Springs we seem to have mild fill soil all over the place because I can run the BW mode everywhere. The difference between Park/M1 and BW is huge. Some of the good targets that show up in BW aren't very recognizable in Park/M1.
In really trashy areas I rotate through all the multi-freqs and the single freqs, I don't trust any of them to get everything. I use MW to re-check areas that have iron signals that sound like machine gun fire, but since it can't be GB'ed I don't push it too far. Weirdly, I find more good targets in 40khz than any other freq.I ran the legend over a part of my yard that was previously un-huntable because it is so full of trash. Full of iron and small to large aluminum can-slaw. It literally bleeps every 3 or 4 inches. I went over it several times in Park M1 and M2 and it showed tons of trash but no legit sounding targets. I switched to Beach MW and pulled 3 zincons in about a 4x8' area with crisp clear signals. I'm a believer. I don't usually hunt super trashy areas but will be doing it in MW when I come across them from now on.