Hi Ciro,
I tried out filter 56MHz_TX_FIRx2_BBPLLx2_ADC_DACx2.ftr. What happened was that application did load the file but the driver did not accepted it as a valid filter. This usually happens when the content of the file does not comply with a filter configuration.
This is the reason why you cannot toggle the button that enables the TX filter. The application does not allow it until a valid filter is configured. It's not a application bug.
I believe that the next step is to figure out why 56MHz_TX_FIRx2_BBPLLx2_ADC_DACx2.ftr is not a valid filter configuration.
Best regards,
-Dan