Is this happening with the webVNC in unRAID? If not, are you connecting to the IP of the unRAID server or the IP of the VM itself?
I am also seeing a similar error, although with the US English keyboard when typing '<' and '5' (on the numpad). This happens with any VNC client, including webVNC in unRAID, when accessing the unRAID IP and port as shown on the VMs page. Due to IP conflicts with a VPN tunnel, I cannot use a direct VNC connection to the VM's IP (although in my testing, keypresses were fine with a different webVNC implementation and other VNC clients connected to the IP of the VM (I just couldn't use the VPN tunnel in the VM... which is the primary function of this VM)). It seems to me like an issue with the VNC passthrough to the VMs in unRAID.