How about multiple versions of the nvidia drivers installed, or maybe both nvidia and nouveau? They could get confused about which one is the boss 
I have a system with nvidia too, and I stopped suspending completely because for me, it sometimes just won’t wake up. A long sleep, you might call it.
The big picture problem is the truly insane complexity that comes with adding a separate mostly proprietary component like a GPU. My distro is derived from ubuntu. Anyone else running a combo like this, I recommend looking up the source for the ubuntu-drivers-common package and especially the file share/hybrid/gpu-manager.c in the source tree.
That can never work.
–
Ian