I was impacted by a Lightning Report flaw yesterday in testing for readiness, and intentionally reproduced it just now. If an existing report utilizes a picklist value, but that picklist value happens to be deleted, that report cannot be run or edited! An error tells you that a picklist value does not exist, but going into Edit mode does not actually give you access to the Filters pane again (see screenshot)?! So as an admin I'd be stuck in a dead end loop on a report, unable to FIX it to run again - and no telling how many users or dashboards rely on this... I'm only able to solve this by switching to Classic and making the fix. Has this come up for anyone else?