xperia lt30p videos won't play

[banjo75]

I have been having issues on and off with the videos I record with the phone then not playing back. Sometimes it's fixed by turning off and on again, but sometimes (right now, for example) that does nothing.
What possible causes, and what can I do to fix it? Extremely frustrating.

[Thommo]

Are your recordings going to internal or SD storage?

[banjo75]

To SD

[_alexdon_]

And does the same occur with videos from internal?