502 for post pages, error reading status line from remote server localhost:4567

[XCTrails]

After an upgrade to 1.13.2 (I think from 1.12.x), I cannot access any forum posts anymore. I reconfigered my apache conf as per the docs - the Websocket passthrough rules definitely weren't required with the old version, but something's not right. I can load the forum main pages, but as soon as I try to load a post page, after some delay, I get a 502 in the browser and this in my apache error log:

[Thu Feb 27 21:11:21.672963 2020] [proxy_http:error] [pid 5133] (20014)Internal error (specific information not available): [client x.x.x.x:62276] AH01102: error reading status line from remote server localhost:4567
[Thu Feb 27 21:11:21.673075 2020] [proxy:error] [pid 5133] [client x.x.x.x:62276] AH00898: Error reading from remote server returned by /topic/19/mapillary-integration-und-trailviews

I'm running Apache/2.4.7 on Ubuntu, there's another (Java based) Websocket server running on another v-host on that box which works ok.

Here's the full conf for the forum v-host:

<VirtualHost xxxxx.xx:443>
    ServerName   xxxxx.xx
    ServerSignature Off
    SSLEngine On
    Include /etc/letsencrypt/options-ssl-apache.conf
    SSLProtocol all -SSLv2 -SSLv3
    SSLHonorCipherOrder On
    SSLCipherSuite "EECDH+ECDSA+AESGCM EECDH+aRSA+AESGCM EECDH+ECDSA+SHA384 EECDH+ECDSA+SHA256 EECDH+aRSA+SHA384 EECDH+aRSA+SHA256 EECDH EDH+aRSA !aNULL !eNULL !LOW !3DES !MD5 !EXP !PSK !SRP !DSS !RC4"
#     Header always set Strict-Transport-Security "max-age=63072000; includeSubdomains; preload"

    # Basic security headers
    Header always set X-Content-Type-Options "nosniff"
    Header always set X-Xss-Protection "1; mode=block"
    
    RequestHeader set X-Forwarded-Proto "https"
    
    ProxyRequests off
    <Proxy *>
        Order deny,allow
        Allow from all
    </Proxy>
    
    # Websocket passthrough
    RewriteEngine On
    RewriteCond %{REQUEST_URI}  ^/socket.io            [NC]
    RewriteCond %{QUERY_STRING} transport=websocket    [NC]
    RewriteRule /(.*)           ws://localhost:4567/$1 [P,L]
    
    ProxyPass / http://localhost:4567/
    ProxyPassReverse / http://localhost:4567/
        
    SSLCertificateFile /etc/letsencrypt/live/cert.pem
    SSLCertificateKeyFile /etc/letsencrypt/live/privkey.pem
    SSLCertificateChainFile /etc/letsencrypt/live/chain.pem
</VirtualHost>

[PitaJ]

Are there any nodebb errors? Can you access those pages of you bypass the reverse proxy?

[XCTrails]

There are no errors in nodebb's log file.

If I change the config.json url to http://<myip>:4567 and try to load that in my browser, I get the main page again, but now 403s and this in the console:

You are accessing the forum from an unknown origin. This will likely result in websockets failing to connect. 
To fix this, set the `"url"` value in `config.json` to the URL at which you access the site. 

That's weird, because for that test, that URL is set to the one I'm accessing it by?!

[XCTrails]

Meanwhile I've reverted to my previously installed version (1.12.0) and everything is fine again. Completely lost here.

[julian]

Sounds like it could be a plugin incompatibility. How were you checking the NodeBB logs?

[XCTrails]

By looking into logs/output.log