Studiomux Effect V 5140 crashin Cubase 11 Pro?

Hi, newbie to Studiomux.

Well, it works fine on my Win10 with Cubase 11 (Studiomux Server5140) for Using my Iphone8 (IOS14, latest Studiomux release) as External Instrument (for example Animoog I can use fine and control it from my DAW via MIDI and record the Audio as well.

But I cant use it as external FX Processor.
What am I doing wrong? It looks easy:
I insert Studiomux Effect as Insert Plugin
and Use Send Device to my Iphone, Channel 1

On my Iphone on Channel 1 I have my desired FX (maybe Blackhole).
It seems to work I see on my Iphone the incoming Signal.

BUT: When I set Receive to my Iphone AND set my Channel 1
the Studiomux on my Iphone STOPS receiving anything (on the receiving side).
In the worst case also my Cubase 11 Crashes!

Funnily it also stops when setting to another Channel (eg2).

What am I doing wrong?
Or is this a bug?

Would be happy for help coz this is such a great App!

Anyone here who might tell me if I am alone with this problem or doing something wrong or maybe there is already a thread which adressese this issue I might have missed?
Would be very happy if someone could tell me soumething about why Studiomux on the Iphone stops receiving when I set Studiomux Plugin within Cubase to receive the signal from the Iphone?