'unknown error' while settin up sync

[i2bator]

When trying to set up Mozilla Sync 1.4 on a fresh install of OC 8.1.2 on my shared webspace (all-inkl.com) i receive an 'unknown error', no matter if i set it up following appropriate steps in INSTALL.md for Firefox 40 or Firefox 28, using a mint email address.

OCs Log says:

{"reqId":"VfHpmVUNlrQAADjaehAAAAAS","remoteAddr":"xxx.xxx.xxx.xxx","app":"mozilla_sync","message":"user.php#140 emailToUserName(): DB: Could not convert email address moz_sync2@mydomain.com to user name. Make sure that emails are unique!","level":3,"time":"2015-09-10T20:35:37+00:00","method":"PUT","url":"/ocld-8.1.2-moz_sync/remote.php/mozilla_sync/user/1.0/2zaci54xcbzgxmgttpn27f7zt3jdd3gv"}
{"reqId":"VfHpmVUNlrQAADjaehAAAAAS","remoteAddr":"xxx.xxx.xxx.xxx","app":"mozilla_sync","message":"userservice.php#169 createUser(): Could not convert email address to user name.","level":3,"time":"2015-09-10T20:35:37+00:00","method":"PUT","url":"/ocld-8.1.2-moz_sync/remote.php/mozilla_sync/user/1.0/2zaci54xcbzgxmgttpn27f7zt3jdd3gv"}
{"reqId":"VfHpmVUNlrQAADjaehAAAAAS","remoteAddr":"xxx.xxx.xxx.xxx","app":"mozilla_sync","message":"userservice.php#46 createUser(): Failed to create user 2zaci54xcbzgxmgttpn27f7zt3jdd3gv.","level":3,"time":"2015-09-10T20:35:37+00:00","method":"PUT","url":"/ocld-8.1.2-moz_sync/remote.php/mozilla_sync/user/1.0/2zaci54xcbzgxmgttpn27f7zt3jdd3gv"}
{"reqId":"VfHpvVUNlrQAAA3ksywAAAAJ","remoteAddr":"xxx.xxx.xxx.xxx","app":"PHP","message":"opendir(/tmp): failed to open dir: Permission denied at /www/htdocs/w0074ac9/ocld-8.1.2-moz_sync/lib/private/tempmanager.php#179","level":3,"time":"2015-09-10T20:36:13+00:00","method":"GET","url":"/ocld-8.1.2-moz_sync/cron.php"}
{"reqId":"VfHpvVUNlrQAAA3ksywAAAAJ","remoteAddr":"xxx.xxx.xxx.xxx","app":"DeleteOrphanedSharesJob","message":"0 orphaned share(s) deleted","level":0,"time":"2015-09-10T20:36:13+00:00","method":"GET","url":"/ocld-8.1.2-moz_sync/cron.php"}
{"reqId":"VfHpwlUNlrQAADjaehcAAAAS","remoteAddr":"xxx.xxx.xxx.xxx","app":"PHP","message":"Array to string conversion at /www/htdocs/w0074ac9/ocld-8.1.2-moz_sync/lib/private/template/functions.php#36","level":3,"time":"2015-09-10T20:36:18+00:00","method":"GET","url":"/ocld-8.1.2-moz_sync/index.php/settings/admin"}
{"reqId":"VfHpw1UNlrQAABYkMoUAAAAL","remoteAddr":"xxx.xxx.xxx.xxx","app":"PHP","message":"opendir(/tmp): failed to open dir: Permission denied at /www/htdocs/w0074ac9/ocld-8.1.2-moz_sync/lib/private/tempmanager.php#179","level":3,"time":"2015-09-10T20:36:19+00:00","method":"GET","url":"/ocld-8.1.2-moz_sync/cron.php"}

any help appreciated!