Instrument names no longer display in this score

I'm hesitant to set the Reproducibility value here, as I don't know how to reproduce it exactly, but I am attaching a file that illustrates the resulting problem.
I created this score using the latest master as of yesterday, Nov 24. I created all the staves from scratch then I copied and pasted notes from another score to fill it out. It looked just fine earlier today. I was re-pasting notes into the guitar staves, because I had pasted tablature and it didn't work right (I submitted a separate issue for that). Then I was messing around with a caesura in the first measure. At some point I noticed that the instrument names had disappeared. I cannot get them to display again. I have tried adding a new instrument, changing instrument names, reviewing all the styles, no joy.
One other thing to mention is that around the same time, when I re-opened the score after an edit and save, the pale blue selection outline/highlight was on the clefs and key/time signatures, not on a note or measure, and it was all staves selected. It looked really strange, and I had to click around in the score to reset the view. Once the view reset, the instrument names were gone.

Maybe a separate issue, but I tried changing the custom page size for this score and it fails. I can no longer set the custom height, nor can I set it to a preset page size like A10. It does nothing. Page Settings dialog maintains the changes, but they do not reflect visually on the screen. I saved the file (after I uploaded it) with A10 as the page size, closed and reopened, but it still looks like an incorrect version of my custom size. This file is corrupted.