CMSIS5: Matrix assignment doesn't work in my code. How to debug?

Matrix assignment doesn't work in my code, seems a very strange bug, probably in my code, but how can I debug?

I tested with CMSIS 5.6 and 5.7

arm_matrix_instance_f32 Hm;
static float H[3] = {0}; 
arm_mat_init_f32(&Hm, 1, 3, (float *)H);
/* ... */
Hm.pData[0] = 0.971422f;
Hm.pData[1] = -0.900052f;
Hm.pData[2] = -0.327298f;
//then here Hm.pData[0] Hm.pData[1] and Hm.pData[2] are always 0
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