If so then simply removing the delays might make it work.

I haven't heard of any evidence that a Pronto is ever able to send keys in a sequence too fast for the normal repeat rate as if holding the key.

Usually sending a sequence with no extra delay has enough delay between steps that it is more than the "correct" (matching the original remote) delay. It usually works because the actual device isn't very picky about the exact rate. But if you added an extra .1 second to a delay that's slightly longer than correct already, the result probably won't work.

I still want to see the Pronto Hex. There are several possibilities for the Pronto Hex needing some tweaking before it could be used correctly in a sequence even without added delay.