Android still uses old ip when resolving hostname
You can  clear arp cache using this command in terminal:

ip -s -s neigh flush all 


(or simply ip neigh flush 192.168.xx.0/yy if you know the network range)

While not necessary, you may need to reboot the device, ping the hostname again and see if its resolved to new IP.

Looking from the other side, you can try resetting winsock entries and TCP/IP stack for the PC and see if it solves the issue.