Thank you so much for your response!
I happened to stumble upon the cause of the issue. It was a blueprint that I couldn’t seem to locate in the Content Drawer.
Initially, I attempted to interact with it but UE kept throwing a bunch of errors at me, so I decided not to touch it.
However, it turns out that the problem was in that blueprint (and my clumsy hands). I discovered this by accidentally deleting it.
It referenced data that wasn’t in the Content Drawer (Matinee Data), which included the sequence interpolation time (it was locked, and I’m not sure how to change that).
I simply started checking all the variables in this blueprint and I found what I needed.
“Preferred Split Screen Num: preferred local viewport number (when split screen is active) the director track should associate with, or zero for “all”.”
After setting the value to “2” and everything returned to normal.