The VstiAutomateDevice don’t work with “vst alias”-instruments. The parameters change only the main instrument although another “vst alias”-instrument was set to “linked vsti”. Is this correct or a bug ?

I tried to use the Device with alias-instruments in Sampletank2 and Kontakt Demo, and they worked fine.

Please confirm the Channel setting of your VSTi again.
What VSTi are you using?

It may be some VSTI does not support multi-channel parameter preference.
In that case it is a shortcomming of the VSTI itself.

I’m using “Symphonic Orchestra Silver Edition” with the Kompakt Sampler from Native Instruments.

Reply from the Devs:

The VSTiAutomationDevice doesnt work with "channels", it only automates the  
parameters that the plug publishes. If all these parameters are bound to the  
instrument that the plug internally handles as "channel 1" instrument, there  
is no way to automate the other channels. You have to use a MIDI CC device then  
and automate the plug via MIDI. This is all up to the plug, we cannot do  
anything here ...