Default State Changing

Hi all, I have an odd problem that I'm having trouble tracking down. I have a report used by a lot of people in the company. When I publish the report, I clear all filters so that the default state of the report is as general as possible. However, recently the default state has changed to a view with multiple filters enabled. I haven't re-published the report anytime recently so it wasn't me. 

After I saw this, I did go ahead and re-publish the report with no filters enabled. Now I'm back in the office this morning and see that the default state once again has these filters enabled.

I suspect that someone has access to edit the report online and is saving the report with their filters. Or that somehow someone's default bookmark is being applied to everyone else. I'd love to hear if anyone has other theories or suggestions for how to track down what's happening and stop it.