Strange and annoying tab key behaviour PT12 Windows

[zillmer]

I have a strange issue with PT12 and Windows 10, although the behaviour also occurred on windows 8/8.1

When running PT with the focus on the PT window, if I press the Tab key it brings up the application switching that would normally be accessed by pressing Alt-Tab. The difference is that unlike alt-tab the open application windows remain on screen and can be selected using a further press of the tab key.

Pressing enter then switches to the highlighted application.

As a result of this behaviour I can't use tab to transient at all.

I have reinstalled PT, trashed preferences, changed keyboard, tried both a wired and wireless keyboard, all to no avail.

Has anyone experienced a similar issue or have any suggestions on how to fix this?