Seconded. In my scenario I only needed to delete the folder rather than reinstall the app, and it was working all new.
It’s quite a serious issue as it happened today when I tried connecting from another plex web client to plexamp, which first broke the visualiser (it got stuck on the ‘music tattoo’ one) as I was unable to change it. Disconnecting and playing local files worked fine, however the visualiser would not change, not via keyboard shortcut or menu. After restarting plexamp I was greeted with a blank screen, yet it resumed music playback grom last time. Media keys were unresponsive. Signed out via the tray icon, but MPD still resumed playing the track after closing and re-opening plexamp while still being signed out.