Final Cut exports not overwriting older export versions

Hi,

I've recently found that when I export my projects out of final cut they're not overwriting the older exports (i.e I've made a change to a title). They start the render process fine and the taskbar says they're rendering but then the file will be done in a matter of seconds saying "share successful" however the file still has the old date and isn't updated....what is going on?

The only other thing I can think affecting this is I recently swapped from "proxy preferred" to "optimized / original" to export it at a higher quality but the exports still come out as if they were proxies. I'm not sure what is going on. So far my only solution has been to save them to a new destination and it works fine, it's only when overwriting that it doesn't work.