Sharing master file issues 10.2.3

I've recently started having issues when sharing master files. The first couple of files I share each day are fine, then they just hang. The background task monitor stays at '0' and although a file registers in the chosen destination it has no content. This happens whether I'm saving them to internal or external drives. If I don't share till late in the day, having worked through a number of edits, this also happens. It's like it just get's bored!

If I reload FCP and share the same file immediately it's fine. It's not related to specific files.

I have not changed any other settings to my knowledge. Same issues apply to sharing direct to YouTube or Vimeo.

Any tips gratefully received.