Can't embed MLClient node with custom knobs in a Group node

[ldmoser]

I have a custom ML model that has inputs, which MLClient created as dynamic knobs.
If I select that node and hit Ctrl+G then I get a pop-up with several error messages of the type:
<node>.<custom_knob>: no such knob

I open the group and introspect the MLClient node and I see it has lost all dynamic knobs and I have to click "Connect" to get them back, with all the values lost.