Seems like something on the one PC is possibly causing the issue.
I would do the factory reset the router, manual load of FW, reset again from the good working PC. When this is going on, be sure to do a Ipconfig /release then ipconfig /flushdns from a command line on the effected PC. Then completely disconnect the PC from the power outlet to be sure that all power drains from the PC for at least 5 minutes and disconnect the LAN cable from the PC. After the router has been re-flashed and setup from scratch and 5 minutes has passed with the PC being fully disconnected from the wall outlet, power ON the PC, reconnect the LAN cable and check the IP address on the PC to see if the address changed. It should have a new IP address and be different.
Test. If the PC still fails and all others work, something on the PC or the adapter with this one PC needs to be looked at. I would get a 2ndary NIC and installed it, try something with a broadcom chipset and test.