http://forum.mikrotik.com/t/cannot-ping-to-mikrotik-from-lan/107918/1
i have similar problem and the author said he was able to do it by adding a mangle rule, but he did not specify the rule for me to see. 
what should the rule to do it?
thank you.
I believe author meant packet marking in mangle section. I don’t know what command he added, but seems you are going to find required info here: https://wiki.mikrotik.com/wiki/Load_Balancing#Firewall_marking