When I expand some tool windows to the work area the drop shadow from the window remains when the window is closed. This shadow is persistent when I close Illustrator and it is seen over all programs and desktop. It even persists when I restart explorer.

The only pattern I seem to find is that it only appears with the toolwindows popping up from the "More options" buttons.

Is it possible this is problem with Illustrator itself of should I search elsewhere for a solution? I have never had this problem before with any other software after year and years of running this set-up. It has only, and still only, appeared when using illustrator.

ILLUSTRATOR:
Illustrator Version: 23.0.3

OPERATING SYSTEM:
Windows 10 Home (Version 10.0.17134)
Systemachitecture: x64
RAM: 16303 MB

GPU:
AMD Radeon HD 7700 Series
Driver Version: 22.19.677.257