I am still trying to find the connection between the theory and the result that I have in the problematic speaker. If there is an issue with the voice coil of the treeter and the impedance is going above the expected 8ohms this will change the cutoff frequency of the filter.
at 8 ohms and capacitor 4u7 the filter is expected to cut at 4.23kHz
at 12 ohms and same capacitor the cut frequency is going down to 2.82kHz
This gives me hope that there could be no problem with the filter
Let's wait for the change and will see.
Thanks once again for all you inputs!