I apologize for not posting the database, the size is too big to post on Access World.
When you have an issue with a database that is quite large, or contains some personal/private info, a common strategy is to make a copy of the database and remove most of the data. Focus on a few test records and "experiment" with a few facts/criteria. If it involves a "complex" query, break it into smaller queries and attack the issue systematically/incrementally. If it's related to vba code, then step through code and try to pin point the issue.
You should be testing on a copy of your database after having made
at least one backup -
things tend to go surprisingly wrong when you test with a live database.
As mentioned, you can post a copy of a test database with only a few records.
You could modify your data in the test database to protect anything personal/private.
Names like Porky Pig, Paige Turner, General Purpose, Owen Money... Central City, Upstate etc. are quite effective -communicate without divulging anything personal.
Also you can anonymize/randomize your data. See this thread for more info on
Randomizing your data.
If you do Randomize-Make sure you are working with a copy of your database.
Good luck with your project.