Plex - Es ist ein Fehler aufgetreten

Hi Guys,
i describe the problem in english but the error message will be german.
since the last update from plex mediaserver to the version 0.9.15.0.1621 i can't play my videos anymore.
i can see the dashboard i can see the movies but if i hit play i got a error message that say something like restart your app, restat your server app and ty again.
the german version is " Es ist ein Fehler aufgetreten beim Versuch das Video abzuspielen. Bitte versuchen sie den Plex Media Server und die App neuzustarten."

If i sync movies to my tablet or phone no problem to play it...only live view is not possible anymore.

as it is shown in the tab.......dpkg -i plex...........everything works fine with the update

ohhh now i want to see how in use the cpu is and i got

No filesystem backend exists for '/dev/root'

Fehler #6000:
exception 'OMVException' with message 'No filesystem backend exists for '/dev/root'' in /usr/share/openmediavault/engined/rpc/filesystemmgmt.inc:226
Stack trace:
#0 [internal function]: OMVRpcServiceFileSystemMgmt->enumerateMountedFilesystems(Array, Array)
#1 /usr/share/php/openmediavault/rpcservice.inc(125): call_user_func_array(Array, Array)
#2 /usr/share/php/openmediavault/rpc.inc(79): OMVRpcServiceAbstract->callMethod('enumerateMounte...', Array, Array)
#3 /usr/sbin/omv-engined(494): OMVRpc::exec('FileSystemMgmt', 'enumerateMounte...', Array, Array, 1)
#4 {main}