I've been having this same issue on my secondary PC for quite some time & have just been putting up with it. Decided to see if I could figure it out. Have tried uninstalling + reinstalling Fences, and deleting Fences appdata, to no avail.
One thing I did notice, is that on the machine that has this issue, it has the yellow/blue shield icon on the rundll32.exe file under System32, indicating that it is going to ask to run as Administrator (left image). The computer that is working normally, does not have this on the icon (right image). So I suspect it may not actually be Fences that is the problem, but rather the rundll32.exe file or Windows. I've read that this was a bug in a previous release of Windows 10, but should have been patched a while ago. Maybe the patched was missed? Both of my OS's are at the same build version.
The message also seems to come up if certain items are opened in Control Panel, like: Keyboard, Mouse, or Sound. Some are suggesting to do a repair reinstall of Windows.
I'll post back if I find a solution other then that.