Not long ago, I was somewhere that had several flat-screen televisions lining the walls. The volume on the tvs was off, but programs were playing anyway, and closed-captioning was used so those watching could know what was being said.
I know that closed-captioning, unlike subtitling, is generally in real-time, but I was still surprised by the number of mistakes -- there were errors in nearly every sentence. Some were really odd, though many were clearly based on phonetic confusions. Sometimes a caption was corrected, but usually the viewer was left to puzzle it out (and to giggle, as in my case).
Here are a few of the wrong captions I recall:
“This sets a bad president” instead of “This sets a bad precedent”
“Now things are under a crowd” instead of “Now things are under a cloud”
“This is about award” instead of “This is about a war”
Bad closed-captioning and bad subtitling can definitely set a bad president.