Splitting SC items in ECS

Hi experts,

We are on SRM 5 ECS.

We have a requirement to split SC items into multiple POs by additional criteria.

We implemented BBP_BS_GROUP_BE method GROUP_PO_BACKEND and set a break point.

The flow is not stopping at the break point.

Are we using the right BADI to split SC items into multiple POs in ECS?

If yes, how can I debug the code?

Any help or guidance would be much appreciated. Irina