I created a project in Project 2016 Standard. I saved the file.

When I reopened it some time later, about half of my tasks had been marked inactive. I am guessing there was some sort of corruption when I saved the file.

I created the file on Project Standard. I have never had anything but Project 2016 Standard installed on the PC I am using. The file was not accessed by anyone else. In short, the file never went anywhere near Project Profesional.