ok so what i've done is this
1) installed the latest (beta 3)
2) detached all peripherals from my mac
3) restarted in safe mode => did not work when I connected the dock
4) detached all peripherals from my mac
5)
How to reset the System Management Controller (SMC) on your Mac
6)
Reset NVRAM or PRAM on your Mac
7) connected the docking station again => did not work
8) also connected the charging cable => for some reason it works now
i really hope i was not just lucky and this helps someone
best of luck