Command 'duplicate entity' fails after undoing last copy. I mean: draw anything, say line. Select this line, than click on 'duplicate entity', click anywhere as startpoint. Now, click somewhere else - line is duplicated, click again and again line is duplicated. But assume last click was in wrong place, so press  CTRL-Z and last copy disappears. Ok. Anything ok to this point. But... duplicate command is still active, so click again anywhere and... no new duplicate. From now on every click is ignored. And of course, command should be still active but should work ;-). Tested on 1.4, linux. If necessary i could test it on windows also.