Strange LAN access error

[Joe Curtis]

On my LAN I have 3 windows 10 pc's, 1 Linux PC( Fedora 25 with apache2), 
1 Raspberry Pi2b (Moode audio) and 2 Raspberry Pi3B's( NGINX), all 
behind a TalkTalk router with a mixture of ethernet and Wi-Fi links. One 
of the Pi3B's is running Cumulus software linked to a weather station 
and has a nginx sever hosting a weather web site 
(www.craythorneweather.info) The other Pi3B has a nginx server acting as 
proxy server to pass weather requests to the weather Pi3 or to a 
community site on the fedora machine as appropriate. The second Pi3 in 
addition to acting as a proxy server also hosts its own (development) 
web site.

I can get to all the web sites externally from the WAN but have hit a 
snag accessing locally on the LAN. Using a browser (Firefox) on one of 
the pc's I can get to the Fedora server or the weather Pi3 server using 
the LAN ip address without a problem, if I try the lan address of the 
other Pi3 the browser appends www.craythorneweather.info many hundreds 
of times to the URI until I get a '414 Request-URI Too Large' error 
message from the nginx server (1.10.3).

Any help getting to the bottom of this problem would be greatly appreciated.

Thanks,

Joe Curtis