This looks to be a common problem with this version, at least for what I've seen. I myself didn't have this problem on my RB750GR3, but also didn't have the balls to upgrade my CCRs on the ISPs that I run. I think that next steps for you would be to put a static IP on your PC and try to connect directly do your MK, maybe trying to connect via MAC to it. If that doesn't work maybe you could try to net install it to a older version and see if that solves anything.
Anyway, a little piece of advise, always have a MikroTik for testing before deploying upgrades. I have an RB3011 and a RB750 just for this. Upgrading firmware on production equipment will always have its risks, so better if you take caution.