InDesign v. 12.2.0.56

I'm working in a book file, and this problem seems to occur at random. The kerning in the first word of a line of justified type is incorrect visually, but when you check it with the cursor, it is the correct number. If you change it, it jumps and appears to be correct again, visually, but if you save, close, and reopen the file, it is incorrect again.

It is problematic because when a PDF is exported, the incorrect kerning is what gets exported.

The problem has occurred in two different books I have worked on with completely different paragraph styles and settings.