Pages is behaving erratically

Thanks for your help.

I upped to Ventura to the most recent version. That change didn't fix the problem. I started doing things like copying the text and pasting it into BB Edit. I ran the gremlin eliminator on the file that that didn't detect any gremlins. In the process of opening a copy of the file in Nisus, I made a docx file. When I opened that file with Pages it seems to have removed something that escaped all the other things I have tried. So I think there was something that somehow corrupted the file.

I hope I can always remember to save a backup file at the end of the day, and start a successor file for use the next day.

I updated Ventura, updated Pages, and zapped the PRAM. That took care of must problems, but the find command was still not always finding Chinese characters. At some point I noticed that the little input box for "find and replace" has a gear symbol by it, and when you open that you find that you can select "whole words." What that turns out to mean is that searching for "anti" will not find "antidote." There must be a space on both ends of the search term. That makes sense for English. However, in Chinese 马 mǎ means "horse." But if you look for that one character with "whole words" turned on it will find 马 but not, e.g., in 新的马车很贵 (New horse carts are expensive.) The reason is that Chinese leaves no spaces between adjacent words.

Thanks to everyone who offered help.