R7900P firmware 1.3.0.8_1.2.1 proxy settings problem with Wordpress Admin running Wordfence

> It seems the Netgear Nighthawk R7900P is not a true pass through
> router for directly connected PCs.

   Define "true pass through router" and "directly connected".  These
routers are NAT gateways, which may not qualify as "true pass-through",
depending on what that means to you.

> [...] Wordpress (WP) site Admin panel protected by a Wordfence plugin
> [...]

   I know approximately nothing about WordPress (except that my
non-WordPress site gets bombarded by people/programs looking for
WordPress-related insecurity exploits).  Does this stuff use any ports
other than the usual web-browser/server 80 and 443?

> The specific problem is that upon logging into the WP site, [...]

   "logging into the WP site" from where?  From within your LAN, or from

the outside world?

> When I put the PC in front of the router to connect directly to my ISP
> and access the Wordpress Admin, everything words perfectly.

   "the PC" is where the WordPress server runs, or where your web
browser runs, or what?  What does "in front of the router" mean?  What
does "directly to my ISP" mean?  Who is your "my ISP"?  How much
equipment is being used other than the R7900P?  What, exactly, is
connected to what, exactly?  If you are cascading multiple routers
(including a device like a cable modem+router), then you could be seeing
"double NAT" problems.