Do you have any resource packs installed? Some older version resource packs might be messing with the text. I don't have the same thing...
Any files? I'll still try to test this out.
Also, was this done on a server? Or was there lag involved in singleplayer? Chunks seem to load faster than I can go on singleplayer.
It's possible that it could've been an update to the newer verisons, but I'll check it out.
All the text shown in the GUI and in the chat looks like instead of §f (White) it replaced it with §0 (Black). You also mentioned you did research and tried to fix but it didn't work? Is there a link to where this case has happened before? I couldn't find anything else.