On mouseover the control buttons show with a soft fade to make them better visible. This fade also appears on top of every other application that is in front of GotoMeeting. This was reproducible in the same call with the Signal Messenger Client v1.40.1 and Windows Paint. As you can see in the screenshot, it does not matter whether or not there is a different application on top of GoToMeeting on the position of the cursor. As soon as the cursor enters the area of the client it is drawn.
I am using the following:
GoToMeeting 10.13.1 Build 18705 without being logged in
Windows 10 Pro Version 20H2 Intel Core i7 8565U with onboard graphics and no external graphics card connected