I also tested it on my hosting account and seems like they’re either testing a new file size limit for HTML and PHP files (not 1 MB anymore but ~110 kBs; that doesn’t even affect JavaScript files) or something else, only affecting these file extensions’ uploads and not renames… In fact I had an HTML file which I renamed changing the extensions during the tests I’ve done and which weighs less than the 1 MB limit, but still more than the new file size limit, and only with JavaScript files did I manage to successfully upload it, despite the file I created just for testing weighed more than 300 kBs. Maybe either renaming the file or, if you don’t want to rename it, splitting it up on different PHP files and including/requiring them on the first one should also work as well, as long as the problem is fixed or the new file size limit for HTML and PHP files is made official, as if it is only the second method will work.