One word, "Vertigo".

Seriously, I believe his perception of "good hits" may have been biased towards what he was hoping for in the heat of the moment. Height may be part of his problem, but it's not the only one. One lung hits also shouldn't be a real problem; not all 5 times anyway. Assuming he is a proficient archer taking reasonable shots, I'd bet his real trouble lies in him being unable to keep his wits about him under the excitement...believing that he's executing a good shot when he is not aiming or following through properly. Unfortunately that trouble is most difficult to overcome.