Did you change routers recently?
That ip address used to be in the designated range of class B addresses, when home routers are supposed to assign what used to be called class C addresses. The class designations aren't used anymore, but something caused the ip address to be re-assigned. Was the 169 address in the receiver, the router or both? If it's both, then the router assigned it. Does your router have the ability to change the range of ip addresses it assigns? I admit, I haven't bought one in 5+yrs but none that I know of ever assigned anything but 192.168.1.xxx, the most common class C address range used for local networks.
Port forwarding isn't going to do anything, since it's supposed to forward traffic on a port to another port. TCP-IP traffic is port 80. Other services like email, telnet, specific gaming use different ports, & don't think there's any reason why you would need to do port forwarding or even if it would accomplish anything.
Is the receiver still set to DHCP server so it takes the ip address that the router assigns?
It's possible you may have visited a web site that did some "hijacking" - who knows.
Unless some service you set the receiver up for, like an internet radio or streaming service, changes the ip address on the receiver in order for it to download content and play it, it shouldn't have changed on its own
I don't use services like Pandora or Pioneer's vtuner service yet so don't know if they would do this or not.
I suggest deleting the ip assignments in your router if that's an option & definitely un-plug & reboot the router so it re-discovers all the connected devices and then you should go into the router config and see what the new ip addresses are. Unless you have some new router feature I'm not aware of, they should all begin with 192.168.1.xxx with default subnet mask of 255.255.255.0.
You may also want to run both an antivirus & malware scan to be sure on your PC just to be safe.