Dear Robert,
This is a side effect of the router star implementation, the router star will discard data coming from an input not connected to an output. When you send a trigger you get samples on all the four FIFOs.
Only the FIFO connected to an output through the router will keep its data.
The router firmware source code will need to be modified in order to keep its data. It is a very simple module, you should be able to modify that easily.
Best Regards,
Arnaud