Android phone fails to communicate using IPv6
I reckon that there is a firewall on your phone preventing the phone from receiving the response message of mac resolution from pc, and probably the firewall levels are different between ipv4 protocol and ipv6 protocol, on ipv6, this level is relative high and block all the ICMP echo request.
The answer above is my assumption, if you totally find a solution. Hope you let me know how to fix it and I have been troubled by this for a period of time until now.