if it's a ISP issue, use a VPN/proxy, if it's a DNS issue use another dns (like cloudflare's or google's)
use a download manager like jdownloader or idm
have you tried all available nodes? some nodes may be overloaded when you are trying to upload. Also lowering the chunk size seems to help
it's an issue with easylist (which is included in the shields) so turning off the shields should fix the issue (you'll see the ads though)