MK,
please can You think about it just a few minutes? 6.41rc61 still the same…!
2 years old bug with TX Rate on all smartphones with android. TX Rate is always only 54Mbps but RX Rate is 72.2Mbps-20MHz/1S/SGI.
http://forum.mikrotik.com/t/xiaomi-phone-low-wifi-tx-rate/93622/1