I can't download the zip file if the file size is more than 2GB
I found the error log server "upstream prematurely closed connection while reading upstream, client:"
Well, 2GB is massive, and it's not unusual that systems have file size limits. This could be caused by your PHP or NGINX. There are loads of results on Google "upstream prematurely closed connection while reading upstream" which might help. This is not caused by Files app and can't be bypassed by Files app.