Why have replay if it is subject to failure?
The replay official(s) is/are no different than anyone else on the crew. Not sure how many perfect games any official has done but I'm still working hard to do mine. Some day with continued studying of the rules, improved mechanics, improved focus at the right spots, etc. maybe I'll get there.
It's been proven beyond any doubt that replay can (and has) corrected many game critical calls. If you expect replay to be any more perfect than the crew on the field then IMHO you're being unrealistic.