I'm having the exact same problem. My speedtest always come out ok. 55 down/ 26 up. But if I actually upload files via FTP, HTTP etc., I can't get any faster than 200kb/s on a good day. It doesn't really matter where I upload to. Verizon Tech Support tells me that this is normal. Speedtest shows everything is so there is nothing they can do. They don't even want to send out a tech to check on my network. I've already received a replacement router from Verizon which of course did not solve the problem.
I also illuminted my whole internal network by directly conncting the Verizon router with a very short coax cable to the wallbox. Even then, upload speeds are still super slow.
I'm very frustrated with this issue since I don't have the time to spend hours on the phone with Verizon doing the same useless things over and over again. I had the same FIOS speed in my previous place and the uploads where blasting fast. So I know it is possible! Is there anybody who knows how to get Verizon to do something about my issue???