could also fix the object in place first with middle-mouse click, and then pin.
or also the old dumb method of quickly let go & pin the object as it is falling.
is sorta finicky for placing on walls, or other precarious positions. but totally works, i just opened up game now to test myself even.
i am pretty sure what the game specifically wants, is the held object to be 100% unmoving first. so for puttin objects onto walls, for me it works really well to push the item into the wall slightly. (push far enough in, and it will stay still against it. but not too much or else it'll start slightly vibrating & physics'ing, failing the "zero velocity" check)
the settings "automatic upright rotation" or the head sway might also be a culprit for messing up maybe?