sonos one gen 1 out of sync to group

What are you listening to?  What speaker is out of sync?

Have you rebooted all the Sonos devices? Are they running S1 or S2, since we’re talking about PLAY:1s?

Note, there was only a single generation of PLAY:1s. They then moved to the Sonos One, of which there was also a single generation. 

Hui running S2 6 other speakers all fine just this particular one has always been out of sync, spotify mainly but does it with amazon and if the soundbar is connected the same, have tried all sorts even connection by ethernet

Refrain from Factory Reset unless asked to do so by SONOS support. Is there any change if you physically relocate the speaker? Is this speaker part of a stereo pair?

Have tried moving it, even tried ethernet connection next to router, and no not part of a paired speaker, has always done this even before we moved house

Have you spoken to Sonos support? A diagnostics report may give them some clues.