Well, having played with this now for an hour, it's pretty obvious that it works OK in auto range (displays the correct DCV) with an initial freq. of at least 2 kHz or higher. It also displays the correct DC or AC voltage reading if not in a dual-display mode, and it also correctly displays the calculated value of a single combined reading of ACV + DCV.
And, since you at least, have the latest firmware ...
Since it's obviously gone through several firmware revisions, and since, even though we are pretty smart people here, it's doubtful we are the only ones who have noticed this since it's been out.
The answer then is that it's acting within it's design parameters. The issue we observe - a dual-display ACV and DCV reading issue of the DCV being wrong (below 2 kHz initially) -->
in auto-ranging mode only, is a specification/limitation that is not explicitly listed in the manual. Many pieces of test gear have limitations and bugs, this is a limitation for this meter.
But, as you realize, and which works, is to simply acknowledge the issue and turn off auto ranging for the DCV second display. All you have to do is up-range it to a higher range and you get the correct reading.