Blank music area

Dorico
1

I just opened a file in Dorico 4 that I was working on successfully yesterday in Dorico 4 (created in probably Dorico 2-something a few years ago), and got this:

Screen Shot 2022-01-18 at 10.07.44 AM
Screen Shot 2022-01-18 at 10.07.44 AM2686×1670 239 KB

Screen Shot 2022-01-18 at 10.07.55 AM
Screen Shot 2022-01-18 at 10.07.55 AM2686×1670 221 KB

Screen Shot 2022-01-18 at 10.07.58 AM
Screen Shot 2022-01-18 at 10.07.58 AM2686×1670 235 KB

Yet the music information is all there, as Play Mode indicates:
Screen Shot 2022-01-18 at 10.07.48 AM
Screen Shot 2022-01-18 at 10.07.48 AM2686×1670 485 KB

And everything plays back fine. Here’s the project file:
Barcrofte O almighty God.dorico (682.6 KB)
This is definitely the strangest thing Dorico has ever done to me. Any ideas what’s going on here?

2

In Engrave mode, the Default Full Score page template set appeared not to contain any page templates – switching it to the Default Part set and back brought them back.

3

Cool, many thanks. I wonder how that happened.