I used OOTHax, although I'm not certain that's the problem. I checked all my files with Safesysupdater, and then launched sysupdater (since there were many posts about safesysupdater quitting mid-way). The downgrade went half way(probably around 20 titles or so). I was fortunate enough that it got to Nativefirm (9.2) before it quit. I tried using Pasta, miniPasta, to install the .cia for the newest sysupdater, but the frankenfirmware wouldn't allow those to run/boot. I gave up on that plan, and tried using SafeSysupdater to finish, but it kept choking at different points (mainly step #5).
Irritated at that point, I simply relaunched sysupdater, and it worked on the 3rd try.
I still ended with 3 mixed titles (Amiibo settings, which you cannot avoid), and two titles that are not part of the downgrade packs being distributed (make sure your pack has 104 titles, so you don't end up with too much extra cleanup work). Most people are ignoring those 3 extra titles and moving on (don't seem to be vital to running emunands and custom firmware). There're other threads on how to possibly clean/replace them (if you finish the downgrade and care enough). Otherwise, be glad and ignore them.