Just wanted to add my experience with my TSU9600 and RFX9400. I tried every option posted in the first post of this thread, but still the connection got lost after the screen of the TSU9600 goes black. Not every time though, but after about 5 minutes of sleep. Very annoying bug, making this set-up useless.

But I found the solution (at least it worked for me!): The RFX9400 needs to be in DHCP mode. In a few other threads I read that static IP is the way to go (and maybe that is true for the TSU9600), but the RFX9400 works flawlessly in DHCP mode!!! No more "command failed" errors at last!

Hope that this helps others with similar problems.