I have never had a problem with iron till yesterday evening. I can relate to your frustration digging deep and finding iron.
Day before yesterday the X70 was humming right along not doing a thing wrong at all, no iron no falsing of any type.
I was feeling VERY confident and felt I was going to smoke my buddy at a small lot that we do, BANG! I get a good 42 from all directions at perhaps 6 inches deep. My friend couldnt hear it I thought this is perfect! I dug my brains out to find a iron nail that sounded sooo perfect in and out of the ground.
I had GB'd, noise cancelled, had my sens real low at about 15 and was running the stock coin pgm due to all the trash and limited time.
Ok, I figured this was a fluke of some sort. I got another hit reading a solid 38, again repeatable in all directions and the sound was perfect. AGAIN a nail at about 6 inches.
This went on for about 5 targets and me trying everything imaginable.
What finally solved the problem was to do a reset of the unit. I defaulted back to factory options for the setup and disc patterns. The same nails in my pouch no longer responded as a hi end coin and I didnt find any more iron either for the rest of the evening.
I doubt I had something set wacky because it has never done this before, I dont mess with the settings and I had used it the evening before with great results. IF I did have it set up weird, the reset resolved the problem. If the x70 got knotted up inside, the reset cleared that problem too.
Hope I never see this iron loving situation again, it was as bad as some say it is, probably worse.