Please check that the NVIDIA Settings app shows Dynamic Twin View as disabled. Sorry; I forget where it is exactly, and can't show you because I stopped using NVIDIA graphics a while ago.
Also, try installing compizconfig-settings-manager. Then go to:
System Settings >
Control Center >
CompizConfig Settings Manager >
Composite
And check the Refresh Rate is the same as what your monitor is using.
Please check that the NVIDIA Settings app shows Dynamic Twin View as disabled. Sorry; I forget where it is exactly, and can't show you because I stopped using NVIDIA graphics a while ago.
Also, try installing compizconfig- settings- manager. Then go to:
System Settings >
Control Center >
CompizConfig Settings Manager >
Composite
And check the Refresh Rate is the same as what your monitor is using.