Multileader does not align to UCS

My multileaders do not always get on the xy plane of an UCS.
Example:
First I set up a UCS (change to front view in WCS, then command UCS V).
When I create multileaders, lines, polylines and text, they end up nicely on the xy-plane of this local UCS with elevation 0.
Everything fine so far..

Then I switch to a different UCS (change to back view in WCS, then command UCS V)
When I now try to create a multileader, it will end up on the xy-plane of WCS.
Looking in the active UCS view it appears as a straight line.
Other drawing elements (lines, polylines, text) align correctly to the UCS.
Is this a bug or is there some setting that messes up my multileaders?