I just experienced the same problem. RB4011iGS+RM running RouterOS v7.14.3. Ethernet ports 1-5 suddenly stopped working. Rebooted the devices connected to those ports but that didn’t make a difference. Found out that I could still access the RB4011 through the devices connected to ethernet ports 6-10 and rebooted it. After reboot, ports 1-5 work normally again.
I made a supout.rif, let’s hope MikroTik fixes this quickly. Never had this issue when it was still running v6.49.13.
Edit: created support ticket SUP-175551.