Cannot produce short crossfades to black

hi there,

just tried to use fades to black:

- put video on track 1
- put black colour clip on track 2
- added crossfade to video on track 1

unfortunately, kdenlive cannot produce SHORT crossfades to black (e.g. 1 second). when i try to do this, the yellow crossfade box does not close with the video on track 2 on the left side - looks like this:

1111111111111
YYYYYYYYYYYYYY
222222222222222222222

this produces a crossfade where very suddenly the video gets darker, instead of doing it smoothly.

what i cannot do is the desired

1111111111111
YYYYYY
222222222222222222222

is this a known kdenlive bug ? is there a way to work yourself around it?