Which version are you using now?
Currently 7.0.4.
Oh heck! That’s a nasty one. 
I think this topic can help (or not!) :
bump
So far some 7.0.3/.02 songs won’t load at all in 7.0.4. So far the only workaround is to load the song in 6.5.4 and resave to a new song. Then the song loads properly, but I lost my channel strips doing that from the save in 6.5.4. I think it’s time to roll back. 
I really like this update except for this and my mix console wiggin out.
OK, can’t explain it but it is very worrying. I have however gone through quite a bit of archived stuff and done a “Backup project” to bring them into C7 versions, and haven’t had any problems reloading them.