As I mentioned, to get any more help here you will need to provide more detail. Other users of course cannot guess the details of what you are doing! You need to give us at least a step-by-step account of what you are doing and how you are doing it… and I mean a detailed step-by-step. Without this, I cannot help any further. For example, you have not once described how you are creating your stems, which is the subject of this thread.