Unable to enable Flash Memory Plugin (method setSettings does not exist)

Hello,

i'm using an RPI2 with a fresh install of the latest stable OMV and have setup everything to my liking except for this one thing:
as the system sits on SD-Card i really want to use the flash memory plugin, but for somereason am not able to enable it.

i obtain the following error message when trying to enable it:

Error #0:
exception 'OMV\Rpc\Exception' with message 'The method 'setSettings' does not exist for the RPC service 'Flashmemory'.' in /usr/share/php/openmediavault/rpc/rpc.inc:91
Stack trace:
#0 /usr/sbin/omv-engined(536): OMV\Rpc\Rpc::call('Flashmemory', 'setSettings', Array, Array, 1)
#1 {main}

i followed the notes that recommend editing the fstab and even though the "before" lines did not exist at all, i created the "after" lines, however without any positive effect to my actual problem.

i also tried uninstalling and reinstalling the plugin, which didn't help either..

thanks in advance for any help given!

after clearing the browser cache the enable button does not even exist anymore.

thanks for your prompt support !