When I upgraded the firmware to the latest RUTX_R_00.07.01, the GPS stops working (posibbly intermittently as it did occasionally work for a while before stopping. I have multiple routers and have tried more than one, with the same result.
I downgraded the firmware to RUTX_R_00.02.06.1 and so far the GPS is working fine now, but I notice that I can now no longer backup the router settings. (nasty error on the web admin backup screen)