What's the artist / album artist metadata for an artist invisible in jremote but visible in gizmo? I think this must be down to metadata, I've had similar where an artist is treated separately as the same value setup as album artist. Eg Abba as artist and Abba as album artist, and you can get albums to appear in one but not the other.
With my own meta data, artist is populated, and album artist is empty, and gizmo/jriver both work no issues.