If you look at the top of the screenshot you can see the menu for "Kate" drawn twice in the top panel. This issue can also be seen in this post. That solution didn't work for me.
What you see is the application menu drawn and "live" where it belongs. Then behind it, it is drawn again, starting from the left side of the screen. It is just pixels, and moving the mouse over them does not highlight them or open a menu.
This only happens after interaction with a widget on the top panel. In other words, if I launch applications from a terminal, and cycle through them, their menus are displayed perfectly. However, if I interact with one of the widgets on the right, the "overlay" problem starts.
I can kill Latte-Dock and restart it and it will be fine again until I interact with any of the widgets.
Now this is interesting and may be related to what the other person posted about this problem. He said that he had the problem when the edit pannel->appearance->background->size was set to 0. If I set it at 30% for example, then the issue happens whether or not I interact with the top panel. In other words, if I kill and restart Latte-Dock, the menus of open programs are immediately drawn twice as is in the picture. However, when size is set to 100%, menus are drawn properly UNTIL I interact with the dock. Then the menus are drawn improperly as shown in the picture. It's as if touching the area reduces the size to something less than 100 and the issue shows itself. Just a guess.
If there is something I can check or more information I can provide, please tell me how to get that information. I'm new to Arch, and new to KDE so I don't know much about this environment. It sure is pretty though!!! Any help is greatly apprecitated. Thanks.