Error by adding block listeners and its execution

Hello, I tried to add a block listener in model's StartFcn (please take look at my simple model file in attachment), but I got a error

Error evaluating 'StartFcn' callback of block_diagram 'simpleMdl'.

Caused by:
Can add listener only when block diagram is executing.

I debugged a little, it seems that error is related to the second block (idx == 2). If I change the idx from [1 2 3] to [1 3], no error happens if I press the model's start button, but still the listener callback won't be executed.

Am I doing something wrong in code? How can I specify the exec. block callback?

Thank you very much.

[Islam Bzhikhatlov]

when I try to read data from joint sensor I got same error, try to read data from another block.

Answer 1

[Walter Roberson]

See https://www.mathworks.com/matlabcentral/answers/35145-error-when-trying-to-use-listner-blocks