Here's the situation - got the PSD list (for example) open and selected on right monitor (although I don't think left or right matters), Hit [TAB]100 to bring up the manual. Reselect the PSD list so the manual is now "behind it".
Power down device. Restart device. Tab 100 is (correctly) still showing at the bottom of the display as an open tab behind the main display. Select it. The tab is blank. You have to then click or touch somewhere in the tab for it to repaint. This happens consistently.
We are on 2.7.2 currently on an Ion W7 but I've just checked 2.7.4 beta on PC and the same behaviour is there.