I don't find mine to be chattery at all. It hits on small pieces of metal. But the only way I can make it chatter is to turn the sensitivity past ten, which is over kill to me. I can run it on ten and it is smooth as a whistle. I too have heard this also but have not experienced it myself. It is a super hot machine!
Mine is only chattery with the sensitivity past 10 or 'in the red' there have been only a few places I can run it near 10, I avg, between 7-8.
I don't recall if I stated this before but My tejon is "Mainly" my relic Machine, as I find it to Sensitive to use it in trashy areas . W/O A VDI Screen.
Don't get me wrong it will work in trashy areas , I just run the main descrim at 'Tab' or above & the Alt disc a couple notches higher. I never really have gotten the Scrap area on the machine tho.
Also never used mine with any coil but the Stock one, I'm 99% sure that in Trashy areas that would help.
? A larger loop = more depth? , Likely, but I usually hunt the Wood's & when set right, I can get CW 58 cal Minnies at / up to 10-12 inches But In most conditions I get most targets (that size) at around 8" or less.
Hunted with a Guy using a GPX 4800 , He was getting 3 Ringers at what I estimate 20" +. I swung the Tejon over them and could hear nothing ..(tried all my tricks) lol, Then put his HP's on & heard that faint Chirp as his coil passed over the deep Minnie.
That's what I would expect from a $4,000 Machine ,W ,after market Coil.
Heck I paid $400 for my tejon used.
Also little or no interference with most other common machines in use today.
Can not say the same for my XLT.
Funny Tho
Every now & again the machine will just 'Chirp' say...Every 12 -15 seconds, & sometimes for a hole hunt.
Usually i'm near a Free Way or another busy highway. Other times it has done this with the closest house being 300 yards away through the Hardwoods.
Then it will quit or I get used to it

Maybe Meteorites or UFO 's have crashed in these places hundreds or thousands of years ago. lol
GL