Unexpected behaviour with ArtNet fixtures

Hi there,
I’ve run into an unexplainable, very unexpected behaviour with the ArtNet part of the DMX Addon:
When using QLC+ to control the 3 ArtNet Nodes (one universe each) everythin works fine and the fixtures are behaving just fine.
If I disable QLC+ and set the same output values through openHAB, the lights just flicker, either every 800ms running the bridges standard mode or at the frequency set as refresh rate.

If I monitor the commands through ArtNetominator or OLA the arrive just fine, but something seems to be different in the commands issued by OH and QLC+.

Does anyone got any idea what may cause this issue?