sun vizor roller blind rear window E39

Since a few weeks my electric sun vizor roller blind for the rear window
doesn't comes up sometimes.
While pushing the button I can hear a "click" but nothing happens.
All fuses are OK.

After trying a week to pull up the sun visor, suddenly when I tryed again
the sun visor comes up.
In the BMW shop they told me that maybe the electric motordrive is broken
and has to be replaced.
The costs will be aproxx. 250 euro's / $ 200

I think if it's broken it won't work at all instead of sometimes it does !

Is this a matter of getting the electric motordrive lubricated....... (how
do I do this, the device is hidden under the backseat-shelf) or is the
device really broken and should replace it.

Has anyone else had this problem and how did he/she slove this ?
Thanks in advance

Sharky
(the Netherlands)