No audio on some recordings

[R+M+H]

Setup:

Sky+ HD, connected via HDMI to Samsung Q90 with audio via HDMI from Q90 to soundbar.

Audio works fine from Sky box playing live TV

Audio works fine from a Channel 4 recording

Audio doesn't work from a Sky Witness HD recording

Audio also now doesn't work from a Sky Witness HD recording that we've watched previously without changing anything.

Any thoughts?

[Mark39]

Does your soundbar support Dolby Digital? If not, check that your Sky box sound setting is 'normal' not DolbyD.

[R+M+H]

Was working, no changes, now doesn't. Checked episodes we've previously watched with no issues and they have no sound too. 

Tried changing sound to normal from Dolby / no difference. Rebooted, no difference.

[R+M+H · Accepted solution]

After leaving it 24 hours, it fixed itself. 

I hate intermittent faults.