I've been experiencing cutoff's mid way through music frequently over the past couple of days. The playlists would get about 2-3songs in before stopping abruptly with no way to resume if on shuffle mode.
I am connected via cable from an Asus RT-AC88U (QoS on/off yields same results) to a Bose Soundtouch 535 with a 1Gbps connection. Spotify sound quality on balanced in the bose app and Automatic on the Spotify app.
Using both the Spotify app via spotify connect or the Bose Soundtouch App yields the same results.
Both Apps are updated to the latest available in the playstore.