There seems to be a problem with worlds containing command blocks in which certain command blocks have stopped working after some of the most recent updates. This issue has noticeably affected command blocks that are supposed to display titles or say text. In some worlds I have tried, the text within the command blocks appears all jumbled up, almost as if the file has been corrupted. I have tried this on multiple worlds and on multiple platforms, and the issue still persists. This may potentially be caused by the Caves and Cliffs update which requires all existing worlds to be made deeper (of course this is just speculation)