EVAL-AD5700EBZ HART OUT Problem

We are trying to use the AD5700 evaluation board to achieve bi-directional communication through HART between an MCU and a PC.
The MCU is connected to the AD5700 through UART (1200, 8o1). Sending data from the PC through our HART adaptor works fine.
The correct UART data reaches the MCU. However, when the MCU responds on UART, the data does not get through to the PC.
 
The connections:
    - MCU TX as output for AD5700 TX
    - MCU RX as input for the AD5700 RX
    - MCU CD reads AD5700 CD and only sends when CD is 0
    - MCU RTS as input for AD5700 RTS and only sends after it sets RTS to low (idle is high)
 
The behavior (jumpers are default.) which we get in full-duplex AD5700 mode:
    - While AD5700 is waiting, CD is low; if we send HART data from the PC, it becomes high and the data reaches the MCU through UART
    - After the complete HART frame is received through UART, the MCU sets RTS high and starts sending, but the PC receives nothing
 
In half-duplex, CD is always high and some data reaches the MCU through UART, but it is not the correct frame; the MCU then does not respond.