The IP address conflicts with the WAN IP subnet. Please enter a different IP address. after reboot

r6300v2

I have a couple of  IPS port forwarded for Minecraft

I accidentally bumped the router causing a reboot, and now the IP for one  Minecraft server is different

I tried to set IP up in the LAN settings to the old IP address, and I get the above message
IP is /was
x.x.x12 to x.x.20
that pc was not originally set up in the LAN settings (which is why it got changed at the reboot)

changed the port forwarding to 12 so it works again, but

trying to keep things organized, and want all my server that can be accessed in the 20-30 range

cannot get it to save in the LAN setting as either 12 or 20

I am guessing some other setting was reset causing the issue and this is just a wild goose chase