Jeff, well I guess it's a good thing that it's a battery issue and NOT an SD Card issue, right? I definitely feel more confident and comfortable about the SanDisk Ultra Plus SD Card that I got for my Mixpre3 from Walmart a few weeks ago, because I think that I won't have ANY issues with that card now, and I hopefully won't have to buy another SanDisk Extreme Pro SDXC-I for my Mixpre3 and can just use and keep the card I got from Walmart!!! Thanks for the heads up and for running some tests for the rest of us!!!
Do get power reliably using the included SD Dual USB A>Single USB C Cable, you HAVE to make sure that the battery can pump out 3A-3.4A total with BOTH USB A ports. Then, plug the POWER USB A port into the highest rated USB A port, usually 2.1A or 2.4A, and then the cable marked DATA into the USB A port marked at 1A.
Otherwise, my USB A Batteries would NOT lower my Mixpre6 properly, or it would go into LOW POWER MODE, and would only allow me to run 2 Channels of phantom power, instead of 4 channels of phantom power FWIW
Hope this helps someone out!
But personally, I won't run my Mixpre6 or Mixpre3 with ANYTHING but Anker USB C Batteries, unless I'm doing a festival and I absolutely HAVE to use my USB A Batteries!
I should have my new Darktrain RT Angle Stubbies early this week hopefully, and I'll definitely be doing some SD Card AND Battery runtimes with my 8x & 4xAA trays, as well as the Anker Powercore+ 20,100mah USB C Batteries!