Hi Nigel,
Before we could determine if you would need replacement for your Surface Go, we would need to perform some troubleshooting which will help us rule out possible software issues. First, install and run the Surface Diagnostic Toolkit. It will get the recommended driver and firmware udpates for your Surface Go and look for other possible software issues. After running the tool, perform a forced shutdown. Just press the power button for about 10 seconds or until the screen goes off. Restart the Surface normally and try to play audio once again.
If the same problem happens, try a different media player. It will also be helpful if you check if the issue will also manifest when playing online video or audio.
You can also run the Playing Audio troubleshooter. Just go to Settings(Windows key + I) > Update & Security > Troubleshoot> Playing Audio > Run the troubleshooter.
Next, try different audio sample rates. Right-click on the speakers icon on your taskbar > Sounds > go to the Playback tab > select the speaker in use > Properties > go to the Advanced tab > try to set different sample rates and bit depths and see if the issue will still be present.
If you still encounter the problem afer following the suggestions, please let me know by replying to this post and I'll advise you about what steps you could take next.
Regards.