Chromecast often stops for periods

[StuartMac]

Both my Chromecast audio and Chromecast video often stop for up to 30 seconds every 2-3 songs when I cast Spotify. On the audio it just stops - on my device the play seconds keep on counting, but no audio. On my Chromecast video it displays the 3 dots - so it appears it is buffering. This happens most times I cast Spotify - only occasionally can I cast Spotify without issues.

No other device I have has any playback issues with Spotify (IOS, Android and Windows Phone 😎 on my network. My Chromecasts also have no issue with any other app (Pandora, TuneIn, Netflix, Youtube etc.) and can stream audio and video fine.

My Chromecast devices are less than 1 meter from my router (the audio is about 200 mm).

Does anyone have any suggestions for fixing or troubleshooting?