Error 'Insufficient Storage' on shared folder

Hello,

we have problem on our Nextcloud installation. After upgrading from Version 10 to 11.0.3 client have a problem with shared folders. Exactly user ‘admin’ shares some folders, but when creating a new folder and putting files in it, the user get’s “InsufficientStorage”, as you can see in the error message:

{"reqId":"CYLEgDM6EKCA05cSwEru","remoteAddr":"95.171.49.193","app":"webdav","message":"Exception: {\"Message\":\"HTTP\\\/1.1 507 Insufficient Storage\",\"Exception\":\"Sabre\\\\DAV\\\\Exception\\\\InsufficientStorage\",\"Code\":0,\"Trace\":\"#0 [internal function]: OCA\\\\DAV\\\\Connector\\\\Sabre\\\\QuotaPlugin->checkQuota('\\\/uploads\\\/afo\\\/30...', Resource id #421, Object(OCA\\\\DAV\\\\Upload\\\\UploadFolder), false)\\n#1 \\\/var\\\/www\\\/wusr35005\\\/www\\\/3rdparty\\\/sabre\\\/event\\\/lib\\\/EventEmitterTrait.php(105): call_user_func_array(Array, Array)\\n#2 \\\/var\\\/www\\\/wusr35005\\\/www\\\/3rdparty\\\/sabre\\\/dav\\\/lib\\\/DAV\\\/Server.php(1070): Sabre\\\\Event\\\\EventEmitter->emit('beforeCreateFil...', Array)\\n#3 \\\/var\\\/www\\\/wusr35005\\\/www\\\/3rdparty\\\/sabre\\\/dav\\\/lib\\\/DAV\\\/CorePlugin.php(525): Sabre\\\\DAV\\\\Server->createFile('uploads\\\/afo\\\/300...', Resource id #421, NULL)\\n#4 [internal function]: Sabre\\\\DAV\\\\CorePlugin->httpPut(Object(Sabre\\\\HTTP\\\\Request), Object(Sabre\\\\HTTP\\\\Response))\\n#5 \\\/var\\\/www\\\/wusr35005\\\/www\\\/3rdparty\\\/sabre\\\/event\\\/lib\\\/EventEmitterTrait.php(105): call_user_func_array(Array, Array)\\n#6 \\\/var\\\/www\\\/wusr35005\\\/www\\\/3rdparty\\\/sabre\\\/dav\\\/lib\\\/DAV\\\/Server.php(479): Sabre\\\\Event\\\\EventEmitter->emit('method:PUT', Array)\\n#7 \\\/var\\\/www\\\/wusr35005\\\/www\\\/3rdparty\\\/sabre\\\/dav\\\/lib\\\/DAV\\\/Server.php(254): Sabre\\\\DAV\\\\Server->invokeMethod(Object(Sabre\\\\HTTP\\\\Request), Object(Sabre\\\\HTTP\\\\Response))\\n#8 \\\/var\\\/www\\\/wusr35005\\\/www\\\/apps\\\/dav\\\/lib\\\/Server.php(231): Sabre\\\\DAV\\\\Server->exec()\\n#9 \\\/var\\\/www\\\/wusr35005\\\/www\\\/apps\\\/dav\\\/appinfo\\\/v2\\\/remote.php(30): OCA\\\\DAV\\\\Server->exec()\\n#10 \\\/var\\\/www\\\/wusr35005\\\/www\\\/remote.php(165): require_once('\\\/var\\\/www\\\/wusr35...')\\n#11 {main}\",\"File\":\"\\\/var\\\/www\\\/wusr35005\\\/www\\\/apps\\\/dav\\\/lib\\\/Connector\\\/Sabre\\\/QuotaPlugin.php\",\"Line\":113,\"User\":\"afo\"}","level":4,"time":"2017-07-06T10:53:10+00:00","method":"PUT","url":"\/remote.php\/dav\/uploads\/afo\/3005540515\/00000000","user":"afo","version":"11.0.3.2"}

As from the log, the client tries to put the files under the ‘afo’ user, but it should save the files to the ‘admin’ user share. Very strange IMHO. The user ‘afo’ is configured with very log quota, as he should always use the files and directories shared bei the ‘admin’ user. But this is not working anymore.

Tried an ‘occ files:scan’, no errors. Cron.php runs every 15 minutes and no errors.

Server ist running on an CentOS 6 with PHP 7.0. Nextcloud ist Version 10.0.3. Clientversion is 2.1.3 (build 8) on Windows 8.1.
Glad for any help to debug this.