Why L1 lights up when L2 is at least in 1%?

[almost]

Signals from Profi are o.k.
Will re-open & double check.

[almost]

"Why L1 lights up & is dimmable only when L2 is at least in 1%?"

and the answer:

"Because + & - of ballast 1 is in Pin 3 & Pin 4 on X104".


Frank, you were right.

Re-open the Matrix and find out that + & - of ballast1 were in EVG on + & - of ballast2 (and of course, vice versa).

Now it is working great and I can play with light colours!