Another thing which I see on the picture is that you are sending MPC clock to OUT_1, this means it will bypass the RK006 clock generator/processor and forwards the MPC midiclock directly to out 1. (If you have set e.g. a clock divider it will also bypass it.)
This is fine if you don't need to sync up a lot of devices but if you want to send clock to multiple outputs it is most efficient to send it to OUT_ALL. This way the clock will be sent once through the usb cable (like here on one port) and distributed within the RK006 on it's clock processor/distributor.
If you then want some ports not sending clock you can block the clock within the RK006 by a filter.
