I’m sure I have seen this previously on here as an issue. The Play:5 Gen 1:

• Has limited memory (32 MB RAM & 32 MB storage),

• Can’t run Sonos S2, and

• Can struggle more with services that buffer large or dynamic content, especially Spotify.

Spotify’s protocol for casting/streaming via Sonos is more complex than that of some other services. It’s more dynamic, potentially sending frequent metadata updates, real-time play-state sync, and album art refreshes, which can overwork Gen 1 hardware.

TIDAL has a simpler streaming protocol as I understand it (especially at standard 320 kbps or FLAC quality) and places less burden on device RAM and processor, so playback can be smoother on older Sonos hardware like yours.

You could try a wired (Ethernet) connection to stabilise things. 

If you’re using Spotify Connect, try Spotify through the app instead. 

Or even restart the router and speaker if they have been running long-term without a reboot.

Thanks for the reply. Interesting to read. I've had this problem for 5 years and now that I tried a different streaming service the interruptions are gone.