I am almost literally banging my head against a wall now. I tried with a VPN from North America, cell, Wi-Fi, and what not, still cannot reproduce. Did you do a good old refresh of the page? Click that reload button?

Just tried 1.3mb file and 123kb file on laptop. Both worked

Also, on a laptop, when doing large files, can you please open the dev console and see what is happening in it? Also check network tab, see if something is hanging