Thanks…might be. I was tinkering around with the setting, but without success.
What I can say now, after installing and testing different OS’s and OpenCV versions, the problem occurs in the combination of an OV5640 Module (maybe some others as well) together with the 64bit Version of OpenCV…
… if a 32bit Version of OpenCV is installed, the C++ Script Video feed is flawless, independently of the OS.
At least I know what to use now… 
[Note: the post @stackoverflow came from myself as well, was just instantly closed… stackoverflow @ it s best 
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