2×2 MIMO Error :stream command was issued in the past

[summer123]

Hello, The 2*2 MIMO I set up uses the USRP-2920.The connection diagram is as follows：

 

When I run the following program,

https://forums.ni.com/t5/Software-Defined-Radio/2X2-MIMO-QAM-with-Alamouti-Coding/ta-p/3507027

I follow the set clock source written on the white paper. The address is only changed elsewhere. However, it was reported that "niUSRP Fetch Rx Data (2D CDB).viERRA stream command was issued in the past."and "Possible reasons:Invalid input symbol array; Input symbol array is empty." I did not find a solution after reading all the comments. Is there any solution? Where did the problem occur?

Is it necessary to match an external clock source? Also, if there is no solution, who can  share the code of the earliest version of this article? Because I saw the previous comment that the original code was not wrong. Thank you! I hope someone can help me.

thanks!