Hello, sadly I've been having exactly the same problem since 5.5 hit... not to mention the error 9006 that occurs every 2 minutes on top on that, which keeps disconnecting me to main menu.

Platform : PC
Connection : Wi-Fi (5Ghz antenna), ~15mb
Client : Not using Steam
Datacenter : Light
Server : Phoenix
ISP : Orange (France)

I've tried contacting the support but they weren't of any help, unfortunately. I'll tell you if I find anything but I'm afraid we'll just have to wait for them to deploy a fix somehow.