This issue was opened almost 2 years ago, and it looks like others have opened quite a few tickets and issues (http://forum.mikrotik.com/t/flow-control-between-css610-and-crs310/171161/1) with zero resolution. I’d call that a complete failure to address the issue at hand. I’ve used dirt-cheap off-brand stuff off of AliExpress that had infinitely better support, there’s just no world in which paying customers should put up with this kind of treatment and end up being suckers.
I for one am planning on getting rid of all my MT gear asap if I don’t hear from them by the end of the year. I’d rather save up and get equipment that is somewhat supported, not this Mickey Mouse stuff. I guess this is the reason why you don’t hear about MT outside of a few YT hobbyists, the company is a joke.