I guess that kind of makes sense... I didn't think about that, probably because, as the video shows, there are about four iterations before slot 2 shows a party; until then it shows "Empty", and only when it does not show "Empty" is it actually loaded. What I thought was happening was that the party members weren't getting saved until the fourth iteration or so.
Upon further inspection and reading, I now realize the purpose and use of the SRAM checksums to check for corrupted save files. So yes, that seems to be what's happening: shorter and shorter chunks are overwriting each other, and the save file gets corrupted, but after a few iterations a checksum collision occurs and then the save file looks OK.
Unfortunately, that's just an inherent problem with the checksum: collisions are possible. I don't really know what to do about that other than maybe add a "saving in progress" flag, if that would work.
We have EVEN MORE themes now, but some old ones are gone...