cross-docking with TRs problem

Hi,

I perform 2 goods movement as follows:

1) move 30 pcs from stoarge locaiton 001 to 002 with MB1B/311

2) move 30 pcs from stoarge locaiton 002 to 001 with MB1B/311

and 001 is WM-relevant storage location, 002 is not relevant

so 2 TRs were created accordingly, (No TOs generated)

and I tried to perform cross-docking using above TRs, but the system can not find matched items. why?

Regards