ownCloud 8.1.2 (rnxtras) fresh install failing

Did anyone manage to install ownCloud above version 8.1 on ReadyNAS R6?

I'm getting some errors from the start. Owncloud was working well here until up to 8.0.X. So I decided to do a fresh install of 8.1.2 (rnxtras), which gave me the following errors:

root@readyNAS:/data/OwnCloud# more owncloud.log 
{"reqId":"lC6uPPrO6EUF\/pAvHmWq","remoteAddr":"192.168.11.134","app":"PHP","message":"Undefined offset: 0 at \/apps\/owncloud\/web\/lib\/private\/appframework\/http\/request.php#685
","level":3,"time":"2015-09-04T18:29:04+00:00"}
{"reqId":"lC6uPPrO6EUF\/pAvHmWq","remoteAddr":"192.168.11.134","app":"PHP","message":"fopen(\/apps\/owncloud\/web\/config\/config.php): failed to open stream: No such file or direct
ory at \/apps\/owncloud\/web\/lib\/private\/config.php#191","level":3,"time":"2015-09-04T18:29:05+00:00"}
{"reqId":"6zhmZ7g2DtsFAQP2rij1","remoteAddr":"192.168.11.134","app":"PHP","message":"Undefined offset: 0 at \/apps\/owncloud\/web\/lib\/private\/appframework\/http\/request.php#685"
,"level":3,"time":"2015-09-04T18:31:17+00:00"}

It seems the config.php file was not writable.

Apart from the instanceid, the config file is empty.

I guess this is triggering the other error about undefined offset at request.php#685, as this line is about the trusted host that needs to be defined in the config file.

After making the config writable, and adding the necessary config, I'm stll getting a blank page. The database isn't created, and the config file seems too empty to be complete.

I know that since Owncloud 8.1, they became much stricter regarding SSL, but my SSL certificate is working fine, as it was before.

I'm getting the following errors in the browser:

• Firefox: Secure Connection Failed
• Chromium: No Data Received, ERR_EMPTY_RESPONSE

I'm wondering if anyone managed to install the owncloud app properly, so I can rule out the possibilty that the problem lies with the ReadyNAS.