This is not atypical. After all, even if you are not working with your computer, the computer (not necessarily Finale) keeps performing clean-up activities on its file system while you are away. Put simply, if you want your Finale files to stay as reliable as possible, save and close them before you walk away. In the long run, it saves time and aggravation.

If you cannot save your file, you may wish to try to export an XML version as a way of retrieving as much information as possible.

Well, this only happens in Finale, and not in other programs. Besides, in older versions I never had this problem.

Others (on the former Finale Forum) have reported this problem in past versions of Finale, so I am glad you have been so lucky in the past. Still, I would recommend not leaving Finale open if you will be away from the program for any length of time.

>If I leave a file open for awhile (I do this a lot),...<

Is there a reason not to use Auto Save? 

https://usermanuals.finalemusic.com/FinaleMac/Content/Finale/Preferences_dialog_box.htm?Highlight=Auto%20Save

Do you let your Mac sleep when idle? That is the most likely culprit. 

I have a number of applications that don't work correctly if my Mac goes to sleep — so I never let that happen.

Oh...both of these ideas show great promise. I'll look for the Auto Save preference, and also tweak the sleep-thing.

Yeah...if possible, I don't want to close the file of an active composition if I can help it. I'm often working on two at a time, but I need immediate access to them when I have a few minutes to compose, or when ideas occur to me.

Thanks~!!!

Yea, if wake from sleep is the real culprit, then MM needs to address it.

It's one thing for me to never let my Mac sleep—I use an iMac. Portables need to conserve battery life.