I’d guess there’s some sort of bandwidth issue or wifi interference going on. In general, those playing music and using a browser would be completely separate things that wouldn’t impact each other.
The first thing I’d try is a simple reboot of the router.
The Sonos stream, even Spotify, works by the controller contacting the computer on the speakers, and telling the speaker a location to get the music from. From that point on, the computer on the speaker is reaching out to your router, and the outward to get the data. After it receives the data, it sends what it is doing to the controller app, but that is not the music stream, just things like the title of the song the speaker is playing, and the album art to display.
Searching on your device would be a separate request from your browser, being handled by your device contacting your router, then going straight out to wherever, and not going to the speaker. So the only place for those two data stream to coexist is on your router. If there’s any sort of restriction there in bandwidth, possibly caused by interference, it should be fixed by clearing that particular device.
