When using two monitors and trying to take a screenshot, this problem occurs, the screen area is simply torn, while the graphics are in their places, if you try to select the area that has shifted to capture the image, a completely different area is selected.
When using one monitor, there is no such problem.
I know this is a slightly older post, but I’ve had this same problem for weeks and kept running into this topic when looking for solutions. Turns out the problem was with KDE scaling, I had it at 125% prior. Setting it to 100% fixed my problem completely (as well as a seemingly related problem in QT Creator where the context menu would be cut off). Hopefully this helps someone in the future. What I did was went back to 100% scaling, then just manually adjusted font sizes so simulate the scaling otherwise. Good luck!