Disable the onboard GPU from the Motherboard bios and check to see if the same issue occurs.
The problem is that the GPU worked fine. Only a few weeks ago it started to misbehave. Now the owner of the local PC shop is testing it. What I realized is that I upgraded drivers from AMD and also downloaded and installed Catalyc software.
After removing the 5450 and deleting AMD software and drivers, I connected an old Tekbright monitor.
However no War Thunder for me. :-)
I'll wait what the outcome of the test is and I'll let you know a.s.a.p. when the defect is known.