One of the very common reasons that puppies try to remove posts is that the post itself has not been inserted all the way to the bottom of the ear and can move around--this provides a real irritant--if the post is placed so that it goes all the way to the bottom of the ear (you can't get it too far down because the canal takes a right angle turn to get to the ear drum--twist the post a little while inserting it. Start the taping of the ear to the post as far down as possible and while you are putting in the first wrap of tape push the back edge of the ear toward the front--this narrows the opening between back and front edges of the cropped ear and makes it much harder to dislodge. I'm dial up so I haven't seen the pictures yet but it sounds like you are only putting wraps of tape at the top and bottom of the ear--I'd sure recommend that the tape be applied at least to the top, middle and bottom and start the posting with the bottom wrap of tape.
Good luck--when you are taping, if you have raw spots, scabby areas be sure you are taping above them and not over them.
dobebug