Board #1 fails to configure the LTC6950 PLL
Cannot configure the PLL, LTC6950. Mattia probed the SPI voltage lines and they appeared low, 2.1->2.2 V, compared to a working board at > 3V.
The PWR_OCXO_EN from the same bank 15 (as the PLL SPI signals) is always tied low, whereas on a working board we can toggle this signal.