iMac with Mojave 10.14.3 copy and paste problem.

Using the mouse cursor, wanting to copy a section of text, there is no shadow beneath the text, yet by eyeball placing of the cursor I am able to extract the text I want. I have run the Activity Monitor "pboard" "force quit" routine as suggested to solve this problem, but to no avail. I have also reloaded Mojave, but still have the same problem. Because there is no underlying "shadow" beneath the text it is difficult to know you are extracting the exact text you were hoping for. For instance on this very message I get no shadow when I try to copy a portion of what we are looking at.

Any suggestions welcome.