first off, i,ll just say, i love the machine..it is finding targets well, but my last 2 hunts, i noticed something weird in Di3 mode..i seem to be having an intermittant(that i can repeat) auto ground balance problem..all my previous and current makro racer 2 and impact, when you hit the gb(auto) they ALL give me the first beep within 1- 2 or 3 pumps, without fail, on my new MMK, it does in the several modes ive tried too..EXCEPT di3, which (in 2 different, mild mineralized soil,ie, 2 schools) it GB'd properly on statup (settings di3,14khz, disc 15 ,gain (what ever,pretty stable at 93+) all other settings stock), so off i,d go searching,when i felt i should re GB, i hit the button and pump 12 or more pumps and still no "beep" i at first figured,maybe its the ground, and went on my way.. several times i retried and maybe once out of 5 it gave me an initial beep and then nothing (if youkeep pumping the impact etc, it will keep beeping)..at the second location, after turning on the machine at startup it GB'd as it should, then of i go again (in my di 3 pattern) again after a few minutes, i stopped over clean ground (like the first location,so i wasnt doing it over metal or whatever,before someone mentions it 
) and viola! same thing again i pumped about 14 times, and was starting to get annoyed, as this was easy ground..but here is what i did this time..in the exact same spot, once it went back into search mode, i flicked up to Di2 and pumped the coil over the same EXACT spot where i couldnt in di3..thing beeped after 2 pumps, and kept beeping and giving a gb value! same thing with Di4..flicked back to my Di 3 pattern and this time it gave me one beep after about 8 pumps then same o samo it did it agian ..As i said, i can repeat this,even did a factory reset and all is good on the initial GB, but hunt for a little bit, and Di3 does it again..unless this is a " feature" im pretty sure that not right..Anyone else have this weird issue??.. Tried to ring makro in Turkey to see if i could talk to someone, but from 3pm their time, the phone was engaged or off the hook .. my dealer i bought it off is over 5000KMS away,so before i send it back to him i want to sus makro out..ive heard all the stories about their good customer service,so if my machine,which i just spent $1100(Australian) is needing a look at, i hope they look after me fairly quick, coz it came straight out of the box this way..i got mine in the first official batches released here, i usually wait with new machines before jumping to make sure the little release bugs are corrected, but i had to have this, as i love my impact, i wanted waterproofing,so i jumped ..this is the first detector ive bought new(over the years), that , if this is a fault,has happened to me
) and viola! same thing again i pumped about 14 times, and was starting to get annoyed, as this was easy ground..but here is what i did this time..in the exact same spot, once it went back into search mode, i flicked up to Di2 and pumped the coil over the same EXACT spot where i couldnt in di3..thing beeped after 2 pumps, and kept beeping and giving a gb value! same thing with Di4..flicked back to my Di 3 pattern and this time it gave me one beep after about 8 pumps then same o samo it did it agian ..As i said, i can repeat this,even did a factory reset and all is good on the initial GB, but hunt for a little bit, and Di3 does it again..unless this is a " feature" im pretty sure that not right..Anyone else have this weird issue??.. Tried to ring makro in Turkey to see if i could talk to someone, but from 3pm their time, the phone was engaged or off the hook .. my dealer i bought it off is over 5000KMS away,so before i send it back to him i want to sus makro out..ive heard all the stories about their good customer service,so if my machine,which i just spent $1100(Australian) is needing a look at, i hope they look after me fairly quick, coz it came straight out of the box this way..i got mine in the first official batches released here, i usually wait with new machines before jumping to make sure the little release bugs are corrected, but i had to have this, as i love my impact, i wanted waterproofing,so i jumped ..this is the first detector ive bought new(over the years), that , if this is a fault,has happened to me 
. Even went to salt water beach and couldn't get it to balance on the dry white beach sand in beach mode. When I got it down to the wet salt sand, and it started really getting static, it balanced perfectly (GB-00) Got out of water and went to balance over dry beach sand and pumped till my arm gave out with no beep... After reading your post, I went out to the yard and found a spot free of metal (I think I'm living at a old dump site. a lot of IRON); Ground balanced at around 70; then at the same spot I re-ground balanced at every program and the only one that wouldn't GB is the 3 Mode. Maybe we can get someone else to verify it with their Makro and see if they have the same results with 3-Mode..... If its a flaw, maybe an update will fix it.... Oh yea and I LOVE my MULTI KRUZER
..yeah, tries mine on the dry sand as well..same result in Di3...