Any Ideas please?

[Samd]

Rarely do I use mp3 but had occasion to download Arctic Lake (nice) in mp3. Problem is that whichever mp3 I play, from this download or the few other mps I have, I get a break in sound of around 1 sec once or twice in any track. I have not gone through all files but the few I tested today have the break at the same time for that file but not the same time as other files. These files are in the same directory on my Synology NAS, as my flac files which never display this break in sound. I have tried downloading again in case of corruption but that made no change. These flacs and mp3s are all via Cambridge CXN and AVR.
Today I tried the same mp3 files through my Oppo and - NO break! Comms for all kit is ethernet.
Colour me stumped!