Just commenting that this was my solution. Updated NC 14 to 14.0.3 while ‘Theming’ app was already disabled and still got this cache issue. Tried re-enabling app, reloaded page, then disabled and reloaded again, which did nothing. Found this comment and commented out cache retrieval (lines 155- 157 for me) from lib/private/URLGenerator.php; refreshed again and there was my favicon. Thanks @stibila!