Render problems AVC Intra

Hi all, I'm experiencing problems when exporting AVC Intra (in my case INTRA CBG100 1080x1980) . Even though I can see my 1 hour long project renders through all the way when I try to open and play the file eg with VLC it does not play.
If I import it back into Davinci I can see that is is basically only rendered about half way, but the file size is identical with other 1 hour long projects Ive rendered successfully before. Any ideas how to fix this? Thank you
If I import it back into Davinci I can see that is is basically only rendered about half way, but the file size is identical with other 1 hour long projects Ive rendered successfully before. Any ideas how to fix this? Thank you