Hi Nick
- how would I know if the track was split?
Just look at the timeline...at each split in a clip there will be an FX box/Loudspeaker /link icon and a blue line.

In the above image the Audio track is also split at these points. However this will not cause it to stop playing unless one of the sections has been muted in which case the loudspeaker will have a red cross...

If on the other hand you see a gap in the Audio track you may have inserted a image or a silent clip. Any gap in the audio track should be easily visible...

If the audio has been split and pushed apart for some reason (it shouldn't happen for an overlay) click the gap and choose to Close the Gap. With an unlinked audio track the gap will close up.
Nat