DMX color item with RGBW LED strip don't send 4th channel

I’ve got some strange problem.

When I use the colorpicker for my RGBW LED strip, the 4th channel (White) don’t getting any DMX channel value’s

I’m using Openhab 1.8.3 with the dmx + OLA binding.

My item:

Color RGBW_LED "RGBW LED strip" (Kitchen) {dmx="CHANNEL[6/4:1000]"}

In the Android Openhab app, I get a Color circle and 2 sliders.
The left slider seems to be the white control, the right slider seems to be the brightness.

When I change the color and brightness, Everything works fine.
But when I use the white contol (left slider), there are no DMX values on the 4th channel.
It seems that the white balance is a combination of the first 3 channels (RGB).

When I use the webinterface of the openhab server, I get a color sphere and 1 slider (not 2!) for brightness. Also here I get no DMX value on channel 4.

How can I get the RGBW LED strip to work properly?
Do I need special configurations to get the 4th (white) channel to work?

thanks!

I did some further testing and i see a strange thing.
when change the 4th channel with a slider (dimmer item) i can see the cange on the OLA dmx monitor from the OLA web interface. but when i use the colorpicker, only the first 3 channels receive a value AND the 4th channel always change to value 0! what can i do to fix this?

Can someone please help me? I can not get this solved :disappointed: