Quite a few slicers throughout a variety of pages in my report stopped displaying any values all of a sudden. I made sure that no relationships were recently changed, and also filters were cleared throughout the report.
The only way to fix this was to simply re-create my page from scratch. Creating a page duplicate keeps this issue.
I think this has been affecting also another issue where an old filter has been persisted through publishing. An old filter that I used weeks ago and published has been persisting despite me saving and publishing WITHOUT the filter.
Anywho, the original issue has got me pretty baffled and frustrated as I don't want to have to worry about slicers not working anymore. I can't identify a pattern to which slicers are affected.
I'd be happy to share my a pbix file with a verified employee and see if this is truly a bug or a user error.