PT12 mouse pointer icon stuck when switching apps

[lewisap]

When I switch to a new app after using Pro Tools 12, the new app uses the mouse pointer icon I last used in Pro Tools. For example, if I use the trimmer tool in PT, then switch to Sibelius, I am having to use the trimmer tool mouse pointer (looks like a square bracket) to edit my Sibelius score, which is really annoying. Sometimes it might be the finger icon, or the zoom icon (magnifying class), depending on what I was last doing in PT. It's really fiddly trying to work in an app with the wrong mouse pointer!
This applies to all other apps, not just Sibelius. But Sibelius is the one where I am constantly changing to and from Pro Tools.
I've tried switching to the finder between switching apps - no difference. I am even having to write this message (in Safari) using the stupid PT magnifying glass!
The only way I can fix this is by going back to PT and choosing the Selector Tool, then the problem goes away. But, as I say, it's intensely irritating!
Mac Pro, Mac OS 10.5.5 (Yosemite)
ProTools 12.2.0