Sometimes I want to change the editing mode from CLIPS to another mode (i.e. volume envelope) and it doesn't work. I click on the "clips" button and the menu doesn't open to give me the menu with all the options. Nothing happens. It feels like a graphics related issue but I am not sure. I cannot always replicate this. 
Is this a known issue?

regards
joni

Is that in the track header, HUD or both?

Shift and left clicking on the required item will also switch the edit filter. Shift and right clicking will switch between the last two edit filter states.