Slider item does not understand IN/DECRESE commands

I got the slider configured in the HABdroid and iPhone Application.
But in the Classic UI the two setpoint arrows for the slider won’t work.

Received unknown command 'INCREASE' for item 'TV_Volume'

How can i use the slider item in a browser?
I use OpenHAB2 and the SamsungTV Binding that is available for OpenHAB2

Number TV_Volume "Volume" {channel="samsungtv:tv:UID:channel"}

Slider item=TV_Volume icon="audio_shuffle_64" label="Volume"

I hope that you might have a hint for that issue.

An older topic which was OH1.x related had a similar issue