August DVB-T Dongle mux scan fails

I had the same problem and it seems that this firmware version doesn’t work. Try one of these versions. It partly fixed the problem for me:
http://palosaari.fi/linux/v4l-dvb/firmware/Si2168/Si2168-B40/

The only problem I have is that it works for a while, sometimes a few days, and then it cannot scan for muxes anymore.

I have to shutdown and restart for it to work again. In theory you should be able to simply unplug/replug the USB stick but I get a kernel panic when I unplug the stick.