I have checked this but could not reproduce this problem. It works fine for me both in AC18 and AC19.
The Project North direction is a Project settings, it is stored within each individual project.
Actually, I am a bit confused about what you write because you are talking about Project North point. There is no such thing, there is only a Project North direction. You can use the Options\Project Preferences\Set Project North menu command to set the direction of the Project North.
After you set it you can go to the Options\Project Preferences\Project Location Dialog and there you will see that Project North value you set. Is this what you are doing? Is this where you see that the Project North value is not preserved when you switch from one file to the other?
Loving Archicad since 1995 - Find Archicad Tips at x.com/laszlonagy
AMD Ryzen9 5900X CPU, 64 GB RAM 3600 MHz, Nvidia GTX 1060 6GB, 500 GB NVMe SSD
2x28" (2560x1440), Windows 10 PRO ENG, Ac20-Ac27