There have been a lot of lengthy solutions to this problem posted here. If this is any help, we have found the same problem while exporting to mp4 via compressor. What we did was to add a filter, any filter will do, to the problematic text clip and bring it’s parameters to 0. This seems to have the effect of creating a more thorough render when the sequence is exported and that seems to have solved our problem with the occasional tile that looks odd upon export.
Hope that helps!