Hey Jared,
Thank you for reaching out to us!
I’ve ran a test and wasn’t able to reproduce the issue you are experiencing in my own WordPress install: in month view, if I filter events by keyword, both past and future events are correctly displayed.
I would recommend you to make sure that all of your plugins are up-to-date. If the issue persists after the upgrade, I would recommend you to run a Conflicts Test. You can start the test by temporarily deactivating all of your plugins (except Modern Tribe plugins) and changing your theme to another one like Twenty Seventeen and let us know if the problem is solved after that (don’t forget to backup your database before changing anything).
If you have any other questions at all please feel free to let me know and I’d be happy to help as best I can!
Cheers,
Patricia