OH 1.8.3 Dimmer no Update from http Binding - why?


I’ve adapted my selfmade CAN based home automation over a selfmade ethernet-can gateway with own software to OH 1.8.3. After some basic starting problems the most works fine at the moment.
I report the actual states from the actuators per one large XML file to OH.
I can switch my switches, dim my lamps and move my rollershutter from oenhab.This all works fine.
If i switch my relays or my rolloshutter from outside openhab, the state ist updated in OH as expected.
But the dimmer state is not updated in OH if I change the state from the local switches.

I’ve added an additional Number item with the same bindig to the item file for testing…
The Number is updated, but the Dimmer/Slider not:

Dimmer        Di_17_01    "Dimmer 1 [%d %%]"                 <slider>      (gTest)           { http=">[*:GET:$s] <[CanCache:1000:REGEX(.*?<dimmer17-01>(.*?)</dimmer17-01>.*)]" }
Number        Test_17_01  "Dimmer 1 [%d]"                    <slider>      (gTest)           { http="<[CanCache:1000:REGEX(.*?<dimmer17-01>(.*?)</dimmer17-01>.*)]" }


Group item=gTest label="Modul Bürotisch"       icon="camera"

The XML reports the state like this:


I don’t know, why this works for the rolloshutter, but not for the dimmer/slider.
Is it not possible to update the dimmer/slider by http binding, so I must read it back to a number and update the dimmer/slider by a rule?

Can anybody help me?