Windows 7: Content search result highlighting not consistent

The highlighting of content search results isn't consistent in Windows 7. When searching for content text across several hundred .doc or .txt files within a single folder, the search result term is sometimes highlighted and sometimes not.

It appears the file names containing the search term are accurately displayed. However if view | content is enabled in Explorer, the highlighted found string and surrounding text are not consistently displayed.

Since you can't reliably see the search results within a surrounding text fragment, this makes it difficult to assess the search results without manually inspecting each file with another program.

Has anyone noticed this? Is there a solution or workaround?

Content indexing is enabled for the file type and indexes recently rebuilt.

Procedure:

(1) In Explorer navigate to the folder holding the .txt or .doc files
(2) Configure Explorer to show content: view | content
(3) Enter a search string for content some of the files will have
(4) Note search results doesn't consistently show the found term highlighted within the surrounding text