Having dealt with Minelab for almost 20 years, one thing I have found is that they are hard to get information out of if you are a general consumer and this is due to the amount of questions that they would be barraged with otherwise. Other manufacturers vary but in general, you will not get lengthy E-mails in reponse to questions you pose . . . . Whites has clearly done things differently with the new Spectra V3 with many of their engineers personnally taking the time to answer questions - even on the forums - and while it has taken a good deal of time for them to do it, it has been a great piece of positive publicity.
I am not doubting that you got an E-Mail but am am doubting that anyone in an official capacity at Minelab admitted to a known inherent issue with the E-Trac to an unknown person not involved in R&D. Before any of us that did work on any of their projects heard a single word from their teams, we had to sign a multi-page non-disclosure agreement.
I believe you misinterperted what they said as to being an acknowledgement of a problem . . if they instructed you to do a RESET (and I hope you understood that to be a MASTER reset and not a FACTORY PRESET reset . . . there is a difference and the MASTER is doing what a reboot does on a computer), they wanted to make sure there was not a software glitch hanging up causing you an issue. We saw that happen several times during the development phase and a MASTER reset usually corrected issues that cropped up and were unexpected.
Air tests on an FBS test are in essence meaningless . . . . and burying a fresh coin is not much better. There have been several tests posted that were done in living rooms or basements . . . I guess if you are looking for coins in that environment that means something but in general, actual long-time buried targets and the response they provide are all that matters to those with time in the field.
Many have posted about finds made with multiple pieces of iron in the same hole as a coin or other keeper. I recently found an 1840 O seated dime with 3 nails in the hole at 6"+. Bryce consistently finds great coins in this condition with his SE and the 10x12 SEF coil so smaller is not always required. I have been doing extremely well with the new 6x8 SEF coil in high trash sites.
I'd urge you to re-read your E-mail and unless it came from someone that was on the R&D team in Australia (since there is no one in Las Vegas that was involved in the E-Trac project anymore), that you see it as one persons opinion . . . . . take the advice and do a MASTER reset and get out and see how it works under actual conditions. Having asked one of these people in Australia the question you said had been answered, I was told they were in fact not aware of any issue as you describe and in fact the E-Trac was tested under just the conditions you describe IN THE FIELD on actual targets that were flagged and checked with various versions of the software (I can attest to that lovely chore!) with positive results.
Let us know if the MASTER reset corrects the problem on actual targets for you.
Andy Sabisch