So this is only happening on this router?
I would start fresh with it, there should be a reset button
Here's the instructions from the manual
To reset the router, locate the reset button (hole) on the rear panel of the unit. With the router powered on, use a
paperclip to hold the button down for 10 seconds. Release the button and the router will go through its reboot process.
Wait about 30 seconds to access the router. The default IP address is 192.168.0.1. When logging in, the username is
admin and leave the password box empty.
Then run the wizard, or set up manually
I suggest that you run the wizard, with a wired connection
Note the procedure in the manual for first time setup