Sync not working anymore (error downloading. Service unavaliable. Operation aborted)

Please help us by providing the following info.

Steps to reproduce
1. Start Sync Program and wait

Expected behaviour
The files from my cloud should sync.

Actual behaviour
The sync process stops at a point and I get some errors and the sync is not working anymore. I can upload files with the web interface without problems.
The errors look like this: http://icecream.me/36260280b24e9a68d41f7a37564450a7

Client configuration
Client version: 2.2.3
Client operating system: Windows 10

Server configuration
Operating system: Apache
Web server:?
Database: mySQL
PHP version: 5.6 cgi
ownCloud version (see ownCloud admin page): 8.2.1
Updated from an older ownCloud or fresh install: fresh 8.2 install. updated to 8.2.1
ownCloud log (data/owncloud.log):
{"reqId":"V8R501UNiPgAAGOkEfgAAAAN","remoteAddr":"80.109.136.130","app":"no app in context","message":"Error while running background job: Autoload path not allowed: \/www\/htdocs\/************\/************\/apps\/files_versions\/command\/expire.php","level":3,"time":"2016-08-29T18:07:15+00:00"}
{"reqId":"V8R6T1UNiPgAAA7KJm8AAAAU","remoteAddr":"80.109.136.130","app":"no app in context","message":"Error while running background job: Autoload path not allowed: \/www\/htdocs\/************\/************\/apps\/files_versions\/command\/expire.php","level":3,"time":"2016-08-29T18:09:19+00:00"}
{"reqId":"V8R6p1UNiPgAACzIIYwAAAAk","remoteAddr":"80.109.136.130","app":"PHP","message":"fopen(\/www\/htdocs\/************\/************\/data\/************Plakat.pdf): failed to open stream: No such file or directory at \/www\/htdocs\/************\/************\/lib\/private\/files\/storage\/local.php#247","level":3,"time":"2016-08-29T18:10:47+00:00","method":"GET","url":"\/remote.php\/webdav************Plakat.pdf"}
{"reqId":"V8R6p1UNiPgAACzIIYwAAAAk","remoteAddr":"80.109.136.130","app":"PHP","message":"opendir(ocencryption:\/\/): failed to open dir: "OC\Files\Stream\Encryption::dir_opendir" call failed at \/www\/htdocs\/************\/************\/lib\/private\/files\/stream\/encryption.php#190","level":3,"time":"2016-08-29T18:10:47+00:00","method":"GET","url":"\/remote.php\/webdav************Plakat.pdf"}
{"reqId":"V8R6p1UNiPgAACzIIYwAAAAk","remoteAddr":"80.109.136.130","app":"webdav","message":"Exception: {\"Message\":\"HTTP\\/1.1 503 Could not open file\",\"Exception\":\"Sabre\\DAV\\Exception\\ServiceUnavailable\",\"Code\":0,\"Trace\":\"#0 \\/www\\/htdocs\\/************\\/************\\/3rdparty\\/sabre\\/dav\\/lib\\/DAV\\/CorePlugin.php(82): OC\\Connector\\Sabre\\File->get()\n#1 [internal function]: Sabre\\DAV\\CorePlugin->httpGet(Object(Sabre\\HTTP\\Request), Object(Sabre\\HTTP\\Response))\n#2 \\/www\\/htdocs\\/************\\/************\\/3rdparty\\/sabre\\/event\\/lib\\/EventEmitterTrait.php(105): call_user_func_array(Array, Array)\n#3 \\/www\\/htdocs\\/************\\/************\\/3rdparty\\/sabre\\/dav\\/lib\\/DAV\\/Server.php(469): Sabre\\Event\\EventEmitter->emit('method:GET', Array)\n#4 \\/www\\/htdocs\\/************\\/************\\/3rdparty\\/sabre\\/dav\\/lib\\/DAV\\/Server.php(254): Sabre\\DAV\\Server->invokeMethod(Object(Sabre\\HTTP\\Request), Object(Sabre\\HTTP\\Response))\n#5 \\/www\\/htdocs\\/************\\/************\\/apps\\/files\\/appinfo\\/remote.php(55): Sabre\\DAV\\Server->exec()\n#6 \\/www\\/htdocs\\/************\\/************\\/remote.php(137): require_once('\\/www\\/htdocs\\/w01...')\n#7 {main}\",\"File\":\"\\/www\\/htdocs\\/************\\/************\\/lib\\/private\\/connector\\/sabre\\/file.php\",\"Line\":268}","level":4,"time":"2016-08-29T18:10:47+00:00","method":"GET","url":"\/remote.php\/webdav************Plakat.pdf"}
{"reqId":"V8R6rlUNiPgAAB9eZeEAAAAY","remoteAddr":"80.109.136.130","app":"no app in context","message":"Error while running background job: Autoload path not allowed: \/www\/htdocs\/************\/************\/apps\/files_versions\/command\/expire.php","level":3,"time":"2016-08-29T18:10:54+00:00","method":"GET","url":"\/cron.php"}

Special configurations (external storage, external authentication, reverse proxy, server-side-encryption):
I have server side encryption enabled.

You have the files_versions app installed?

Before looking for more bugs, you are still using version 8.2.1, the current is 8.2.7 and a lot of bugs have been fixed since then.

Is this your own server? Then I would use system-cronjobs as well.

thanks for the answer!
I just updated to 8.2.7 but I still get the same error.

Yes I have the files_versions app installed. But also when I deavtivate it, I get the same error.

No its a shared server but I have ssh access and I can setup conjobs. I set it to "Web Cron" now.

Do you know what else I could do?

Do you still get this one with the new version?