Elektron Musical Instruments

I recently purchased a used machinedrum (sounds great, interface is a
dream!, etc.)  I immediately/successfully upgraded its OS to 1.19c.  

After a few days with MD and headphones only I finally tried to use it
as a master clock with my other machines...
this is the 'problem':
The MD "always" sends out its MIDI clock - even when it is stopped. 
(So, as a master clock it is useless becase my other
sequencers/machines are constantly running and wont stop.)
I set my MD MIDI-output to MidiOX and I see a constant stream of MIDI
clock data.

Is this normal? 
I would appreciate any comments before I contact Elektron.

Best Regards
Chris