I've recently noticed that JRemote 3.0.8, and possibly earlier releases, have an issue when music is added to the library. The "recent" view has nothing but a white rectangle for the album art and when the item is accessed, a window pops up saying "No content found here." When I go to the "artist" or "album" view the newly added content is there as it should be.
This doesn't happen on all newly added content and MC itself, 20.0.21 in this case, never has the issue.
Take care!