This hadn't been the case prior to the 2019 update, and having hundreds of clips in some projects, this has already become a big nuisance for going through footage. Normally, I'd shift+1, press the down arrow, and shift+o to bring the next piece of footage from the project panel to the source monitor to pull selects from, but that no longer appears to work. Is it possible an option I don't know about got reset or is this no longer possible?
Sorry for the trouble with workspaces. It's working in my machine. Are you on a custom workspace or custom saved Keyboard shortcut layout? If yes, change back to default and check the issue.
If the issue persists, reset the preferences and see if it fixes the issue: FAQ: How to reset (trash) preferences in Premiere Pro?
Let us know the status.