For anyone who may find this information useful in the future, I found what I believe to be the solution.
During my rolling upgrade from BE 10d to 12.5, my selection lists were lost, though backups continued working. The result of this was simply that I could not edit my selection lists, which would probably eventually cause a problem, but it was fine at the time. Fast forward 7 months and I finally got around to recreating all of my selection lists. However, I did not delete the old ones; I just edited them. I figured that since nothing was selected, they would not retain information from the old lists. I was wrong. :) I had to delete the old lists since there was no way to deselect the old data and create the lists from scratch.