One prevailed problem of Dollyeo Chagi, perhaps it must be in every kicks, is what you can see that in the movie above.

He makes too distinct movements for a Dollyeo-chagi, separating every step. Thus he comes to make several movements for a dollyeo chagi. He fails to speed up in his kick, for he has to make several movements.

I mean, the kicker stops when he kicked the target and, stops again when he folded his knee after kick, and drop his foot. This motion may seem to be exact in some sense, but practical. The whole motion of kicking and getting back to the next ready pose should be continues one, to be fast. See, for an example, this(He improved later as I pointed out his problem).

Every motion of attack and defense is one, and it should be the simple and sudden one. Remember, "Everything ideal is essentially simple, in which difficulty and easiness are same."(PPT, Ch.24), and "Simple motion is in an instant. It precedes the opponent's reaction because it doesn't hurry yet connects necessary movements only. Therefore, even though you move slow he cannot defend it."(3JKY, Ch.3-6)