With a lot of standard reports in the CRM they are filtered to the current record you are looking at (e.g. the Quote line report on a quote record, or Sales Transactions on a division) by use of a standard filter.
It is possible for a user to remove or toggle the '<Record ID> filter is from a page argument' filter, which causes unexpected results and is not obvious how to remedy (via resetting the report to public).
It would help if the ability to toggle/remove this filter was disabled.