Answer:
It might be advisable to (de)activate the hardware acceleration.
In RFEM and RSTAB, you can activate or deactivate the hardware acceleration (OpenGL) using the menu "Options" → "Program Options" in the "Graphics" tab of the dialog box.
Furthermore, you can set the improved smoothing (antialiasing) in the same dialog box to prevent the edge effect. Both options are only activated after restarting the program.
The problem could also be that the graphics card driver is outdated. Under certain circumstances, this may lead to problems when using RFEM and RSTAB. Therefore, please update the driver.
