Nuendo 7 (sierra) log me out...

Perhaps someone can help me, I’m running Nuendo 7 (latest update) over Sierra 10.12.6 and 5 o 6 times a days Nuendo crash and send my my mac to Log In window, I’ve notice that it’s connected with track version in midi files, the system begins to run really slow till I duplicate or delete a trackversion, after that it runs fine till the next track version problem (let’s say a few minutes) any idea?