If you group any mmc.exe windows like computer management, event viewer, device manager, active directory users and computers, etc... the windows will not ungroup individual windows when you the 'only group when the right mouse button is also held down' option selected in groupy settings.
I believe I have observed the same issue with other applications, but only took a note about mmc.exe.
I also observed that the windows shortcut for task manager CTRL-Shift-ESC is caught by groupy when teh 'group newly opened windows if the Ctrl key is held down whilst opening them' option is used. I understand this is not a glitch, but perhaps it shouldn't group windows opened by hotkey combos and only group if the only hotkey used is CTRL.
Environments:
Windows 10 Pro 1703 running Groupy1.12rc
Windows 10 Pro 1709 running Groupy1.12rc