Windows 2012 R2 start button not working over RDP

It seems that when I RDP to some 2012 R2 machines, the start button seems to become un-responsive (Highlight doesn't even appear over the icon).

Failing over to ye'old ALT+Home still works a charm however.

A reboot resolves the problem, but it does intermittently return after. Has anyone experienced this or knows how to fix without rebooting production servers.

I see the same problem, and found a workaround by moving the task bar to the left or right side of the screen, and suddenly it Works Again. (moving it back to the lower left corner, breaks it Again)

I have the same problem. If you open task manager under details, there are 2 explorer.exe running. End both tasks and run new task type explorer will work.