According to the forum page for Brad O, he was last active "June 14, 2019, 09:29:26 pm". His last post here seems to be June 7. He has not answered a private message I sent some 10+ days ago. Maybe the Danaher Group don't find it profitable to let him use his time here
My DMM6500 works OK out of the box (Calibration dated March 2019). It has survived 3-10 black- and brownouts a day. It even runs on down to 160-70 volt AC line voltage (I live in the countryside in not particularly developed NE-Thailand).
------ EDIT August 15 ------
Yesterday I sent a an email to Tek support just to try once more. This time I got all my 3 cases solved in a matter of hours. So I must change my view of the support given by Keithley/Tektronix US this time to a very positive one. I do however write "US" (i.e. Americas) above because I have not changed my view on support emails I got from China/Singapore.
So I am now quite a happy user of DMM6500 with full calibration data and Kickstart running. Let us hope Brad O or another Keithley representative comes back here so that the forum can report bugs in a single place.
- END of edit
- ORIGINAL post continued - but I am quite a lot more positive regarding support now:
I probably will never change firmware or program the box. Why? Because over the last 2 weeks in some 30+ emails back and forth with "support" persons in Keithley / Tektronix / Fluke (all Danaher) that redirected me around from Shanghai to Singapore to Thailand to the US and back and around and ... again and again, I have lost all hope of finding anything that (imo) even only remotely could be labeled helpful resulting from opening a support ticket. But I am OK. With the good reference manual, you will do fine as long as the box works. If it stops working - well, then ...
Good luck
- END of old post - please see EDIT above as I have changed my view since writing this.