hey, I have the exact same problem! just bought premium membership to raise up download speed and while smaller files were downloading without any issues, the large files were capped at around 10-70kb/s from European servers and around 300kb/s from American. I've found temporary solution via turning VPN on, now I can download with more or less accepable speed (around 1 mb/s) but honestly it still sucks cause I paid for unlimited speed and I got this turtle crawl instead. I'm wondering what causes this thing and how to fix it as well.