It does. I changed it to Full Screen and it goes full screen. Or changed it to None, and nothing happens.
I thought of this too and have had it happen many times in the past. I keep testing very very carefully to make sure it's a single click. I even tested with the Windows 7 Mouse double-click setting test. It only shows a single-click happening.
Okay, this was it. When I disabled your Viewer Select script, the problem goes away.
I believe this also only started with 12.3.3 but I can't be 100% certain because I think I skipped 12.3.2