Based on the instructions I received from FM Tech Support, I was able to find the items modified. It's a very long file. The summary described 2 items "modified", but doesn't say what they are. The log shows quite a few "changes" to several themes. I believe the solution uses a modified of only one of those themes.
If only the themes are damaged, it seems to me that the problems with this file could be easily corrected by using a different theme. Hard to understand why this would cause the Recover command to conclude that the file should not be used, given the time and cost of rebuilding everything since the last build I worked on last spring. Or why I should get two different results on whether there was any damage at all when running Recover a second time a month later.
I don't expect this feature to be perfect. Though I do expect it to be accurate and consistent.