720. Windows 10 Start Menu and Search Icon will not work first click

For some reason yet not discovered, clicking the Start button or Search Icon button results in nothing happening. Click it a second time and it works. I have noticed that after any new window is opened, clicking the mouse on START or SEARCH Icon results in nothing. A second click must be done to either to get them working again. After that they work as long as you click within 4 seconds of closing the Start menu. Otherwise, it is back to not working. Bypass is to RESTART. However, one time it just started working correctly again! This problem is just a nuance and not worth my time, at least at the moment, to debug further. It happens rarely and RESTART clears it.