When logged in no link can be accessed

[Ondrej Tokár]

I have installed NodeBB recently on my Windows 2012 Server running it on IIS 8 with reverse proxy.

It all seemed to be working well until some point when it broke. Now when I am logged in as any user, when I click on whatever link on the forum or navigation icon, it starts loading and in 3/4 it stops and hangs there. Meanwhile I can see these errors in the console log:

 WebSocket connection to 'ws://forum.maguss.org/socket.io/?EIO=3&transport=websocket&sid=StguwnFo7hgYtRZ-AAAV' failed: Error           during WebSocket handshake: Incorrect 'Sec-WebSocket-Accept' header value
 nodebb.min.js?854c9538-dcab-4d8f-adca-92a828835134:12 Uncaught TypeError: Cannot read property 'uid' of undefined
 nodebb.min.js?854c9538-dcab-4d8f-adca-92a828835134:10 Uncaught TypeError: Cannot read property 'uid' of undefined
 nodebb.min.js?854c9538-dcab-4d8f-adca-92a828835134:5 WebSocket connection to 'ws://forum.maguss.org/socket.io/?          EIO=3&transport=websocket&sid=e-gZbMkSkfMS-xWrAAAb' failed: Error during WebSocket handshake: Incorrect 'Sec-WebSocket-Accept'      header value
 nodebb.min.js?854c9538-dcab-4d8f-adca-92a828835134:10 Uncaught TypeError: Cannot read property 'uid' of undefined
 nodebb.min.js?854c9538-dcab-4d8f-adca-92a828835134:5 WebSocket connection to 'ws://forum.maguss.org/socket.io/?     EIO=3&transport=websocket&sid=_UIzXZWxyiHmYG4KAAAh' failed: Error during WebSocket handshake: Incorrect 'Sec-WebSocket-     Accept' header value

I am not sure what is it related to as I haven't done many changes after starting and what I have done I tried to revert (search and color plugin installs).
All the links and navigation works just fine when I am not logged in as an user.

I have tried to reboot the server same as nodebb.

Any ideas? Your help would be much appreciated!

EDIT1:
I had my colleague try it too and it works for her just fine even when she is logged in. However another colleague who was logged in at the same time when I was has the same issue as I have.

Plus as a bonus when I open admin panel it seems like nothing is there. No custom CSS that I added, no custom headers or anything like that. But the effect of it is applied on the forum itself. For clarification I give an example:

I have changed color of all links from standard Darkly skin from cyan to orange in the custom CSS via Admin panel.
I got it applied, working just fine.
I discovered the issue that I am describing above and when I open admin panel now I can't see any custom CSS nor HTML headers in there.
Even if I refresh cache, the Orange links are still on the forum, meaning the custom CSS remained, but it's not showing in the admin panel - custom CSS.
And also when I am logged in into forum and I try to open admin panel it gives to me a login form like I wasn't logged in. When I fill it out and submit, it shows white blank page saying: "Forbidden".

EDIT2:
I tried to reinstall it from scratch with a downgraded version 1.1.1 and it was again working for a while (about an hour) then the same issue appeared.

EDIT3:

How is it possible that not even official forum functions properly? I added updates, refreshed the page several times also with shortcut: alt+shift+r, but I can't see the updates applied. Though I can see updates when I press edit on the post.