Have had no time to consider the Genius this month but when I saw your posting today I had a quick glance at it. Is it (en)cumber for 23 ac, dropping the 'en' for the 33 letters that form the group of 5? Um and er would be the double hesitation.
This might be totally wide of the mark, as I have not even tried to complete any part of it yet, in which case apologies. I have previously found enigmatist's instructions hard to fathom.