Missing documents in the views

All documents in one of our custom developed database cannot be seen from the views on Mondays. They can only be viewed in temporary views with no selection criteria. A schedule fixup task runs on every Sunday night. I’m not sure if the fixup caused this problem because when I manully ran the fixup for the database, everything works well. At first, I thought these documents were deleted so I copied them from the Friday back up. As a result, there are duplicate documents in the temp views. I compared the document properties of the documents that don’t show up in the views with those that do show up in the views, and I couldn’t find any difference except the documnet create dates. This has been happening for 4 weeks in a row on every Monday since we upgrade our server to 6.0.1. Any idea what cause this problem and how do I fix? Thank you.