Getting a “Changes you made will be lost” dialog prompt on a custom post type page

I have a simple custom post type setup with a few custom fields. All seems to be working ok until on the odd occasion I get the dialog box you normally see if you try to navigate away from a post/page with unsaved content. I am trying to navigate away from the page which is what triggers the dialog prompt – but I have already saved my content.

Has anyone previously come across any issue like this?

I think it’s isolated to my custom post.

Managed to solve this after I got lucky with a random search and found this.
Post metadata deletes itself

There’s also a decent thread on the problem here:
https://stackoverflow.com/questions/2539951/wordpress-add-meta-box-weirdness