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fmcomms5 rev C problems with setting the rf ports

Good Evening,

I am working with an FMCOMMS5 EBZ rev c using no-os, and I have a few questions about the ad9361_set_rx_rf_port_input function.  The input mode options are A_BALANCED, B_BALANCED, C_BALANCED, etc.  My FMCOMMS5 board only has 4 physical rx ports (RX1A_A, RX2A_A, RX1A_B, RX2A_B).  A picture of my board is shown below.

I have DDS tones transmitting out of all 4 tx ports with cable loopback into the 4 rx ports (not shown in pic).  A_BALANCED is the only mode where I have all 4 tones hitting my ADCs.  B_BALANCED and C_BALANCED modes do not receive any tones on any rx channels.

Would B_BALANCED mode be for the 4 rx labels with missing ports (i.e. RX1B_A, RX2B_A, RX1B_B, RX2B_B) beside the tx_mon diagonal ports? To me, that would explain why I am not seeing anything.

If that is the case, which ports correspond to C_BALANCED mode?

How would not having C_BALANCED mode affect the functionality of ad9361_fmcomms5_phase_sync.c, specifically in the configure_ports function where, at a lower level, the ad9361_set_rx_rf_port_input function is used to configure to C_BALANCED mode?

Here is the reference for the ad9361_set_rx_rf_port_input function.

 * Set the RX RF input port.
 * @param phy The AD9361 current state structure.
 * @param mode The RF port.
 * 			   Accepted values:
 *				A_BALANCED (0 - (RX1A_N &  RX1A_P) and (RX2A_N & RX2A_P) enabled; balanced)
 *				B_BALANCED (1 - (RX1B_N &  RX1B_P) and (RX2B_N & RX2B_P) enabled; balanced)
 *				C_BALANCED (2 - (RX1C_N &  RX1C_P) and (RX2C_N & RX2C_P) enabled; balanced)
 *				A_N		   (3 - RX1A_N and RX2A_N enabled; unbalanced)
 *				A_P		   (4 - RX1A_P and RX2A_P enabled; unbalanced)
 *				B_N		   (5 - RX1B_N and RX2B_N enabled; unbalanced)
 *				B_P		   (6 - RX1B_P and RX2B_P enabled; unbalanced)
 *				C_N		   (7 - RX1C_N and RX2C_N enabled; unbalanced)
 *				C_P		   (8 - RX1C_P and RX2C_P enabled; unbalanced)
 *				TX_MON1	   (9 - TX_MONITOR1)
 *				TX_MON2	   (10 - TX_MONITOR2)
 *				TX_MON1_2  (11 - TX_MONITOR1 & TX_MONITOR2)
 * @return 0 in case of success, negative error code otherwise.