The errors are all warnings and I get emails like this 2-3 times per week. I won't be able to correct the errors every time before DW will replace the links that need to be changed.
Consequently, I tried it in Brackets without any changes and it matched all 13 occurrences.
Is it possible there is some setting incorrect in DW? I prefer DW over Brackets so I still want this to work, if it can.
Code issues can definitely cause DW to act up, but since it does work in Brackets (not sure if they have the same F&R tool) that would make me lean toward something going corrupt in DW itself. I'd try clearing the program cache and/or renaming the personal configuration folder as my first steps...
Clear Program Cache - https://forums.adobe.com/thread/494811
Rename Personal Configuration Folder - https://forums.adobe.com/thread/494812
Those tend to catch a lot of funky "just started happening" style behavior in DW.