Filter returns less results than slice
I ran across a fun one... An agent reported seeing some, but not all, opportunities in a report. There is an opportunity workspace rule that assigns an opportunity to account "Contract Admin". I'll skip all of my trouble shooting steps, but the thing that helped me identify the issue was to add accounts.acct_id (entity id) to an All Opportunities report.
When using a filter to narrow results, I get back only opportunities assigned to the correct "Contract Admin" account. When using a slice to narrow results I get back all (the desired results, about double the records) opportunities assigned to "Contract Admin" but since I added the entity id column I can see that there are two different "Contract Admin" accounts. I'm guessing at some point the contract admin account got deleted and re-added. The auto assign rule was still assigning new opportunities to the old deleted account.