Importing Polywaves into Audacity

I use a Sound Devices MixPre 10ii to record local amateur classical concerts. I just started to use 10 channels (instead of only 8, which I have used for years). I typically use Audacity to edit.

My practice when using 8 channels is as follows: Open (in Audacity) the first MixPre 10ii wav file (usually there are 2 - 4, because concerts run from 1 - 2 1/2 hours). That typically gives me 8 tracks in Audacity. Then import the second file, which gives me 8 more tracks. Then I append the first track from the second file to the first track in the first file. Repeat for all tracks. Same for third file, if there is one.

So, I wind up with a single, continuous track for the entire concert, for each of my mics.

Over the weekend, I recorded a concert using all 10 channels of the MixPre 10ii. (Used the unbalanced aux inputs [from two more spots] for tracks 9 & 10). It worked fine.

I imported the first file. Got 10 tracks, as expected. Then, imported the second file. Got only 8 tracks. Tracks 9 & 10 form the second file simply were not there.

I scratched my head, and abandoned the project. Started over. First, imported the second wav file. Got 10 tracks, as expected. (This was the file that was the second file imported, as described above.) So, the 10 tracks are there. Then, I attempted to import the first track. Got only 8 tracks.

I asked about this on the Audacity forum, but that is not paid support, and there is no guarantee of getting any answers. (So far, I have had no answers.)

Anyone have any ideas?

Or know of a way to buy support (I am willing to pay for an answer).

Thank you for any comments.

DG