Problem with Gitlab/Mattermost on Centos 6 with SCL Apache 2.4

I'm having the same issue with Apache 2.4.6 and CentOS 7 with https.
"Please check connection, Mattermost unreachable. If issue persists, ask administrator to check WebSocket port." message and all connections through wss:// return 301.

<VirtualHost *:443>
        ServerName mattermost.example.com
        ServerSignature Off

        # TLS
	SSLEngine on
        SSLProtocol all -SSLv2
        SSLHonorCipherOrder on
        Header add Strict-Transport-Security: "max-age=15768000;includeSubdomains"
        SSLCompression Off
        SSLCertificateKeyFile /.../privkey.pem
        SSLCertificateFile  /.../cert.pem
        SSLCertificateChainFile  /.../chain.pem

        ProxyPreserveHost On
        RewriteEngine     On
        SSLProxyEngine    On

        RewriteCond %{REQUEST_URI}  ^/api/v1/websocket      [NC,OR]
        RewriteCond %{HTTP:UPGRADE} ^WebSocket$             [NC,OR]
        RewriteCond %{HTTP:CONNECTION} ^Upgrade$            [NC]
        RewriteRule .* ws://127.0.0.1:8065%{REQUEST_URI}    [P,QSA,L]

        RewriteCond %{DOCUMENT_ROOT}/%{REQUEST_FILENAME}    !-f
        RewriteRule .* http://127.0.0.1:8065%{REQUEST_URI} [P,QSA,L]

        # Be sure to uncomment the next 2 lines if https is used
        RequestHeader set X-Forwarded-Proto "https"

        # Prevent apache from sending incorrect 304 status updates
        RequestHeader unset If-Modified-Since
        RequestHeader unset If-None-Match

        <Location /api/v1/websocket>
                Require all granted
                ProxyPassReverse ws://127.0.0.1:8065/api/v1/websocket
                ProxyPassReverseCookieDomain 127.0.0.1 mattermost.example.com
        </Location>

        <Location />
                Require all granted
                ProxyPassReverse http://127.0.0.1:8065/
                ProxyPassReverseCookieDomain 127.0.0.1 mattermost.example.com
        </Location>

        ProxyPreserveHost On
        ProxyRequests Off
		
</VirtualHost>