Please lower the PHP limits. The problem is that it tries to pack the complete file into the POST body and not to split the file into smaller packages.
It is best to set the limits to a maximum of a few hundred MB.Otherwise, it should be a problem that you can no longer upload files to the WoltLab Gallery. Please check the server error logs, further information should be available there. Probably a limit is reached by the web server (not PHP).
As long as I can upload 3.29MB movies to the woltLab Gallery on the forum, I don't have any server problems, I have a private server.