Tvheadend

i have a skystar usb 2 hd ci tuner.( fw: dvb-usb-az6027-03.fw , dvb s/s2, working with tvheadend fine)
no problem mux and other function but some muxs symb rate <5000 and in terminal dvbsnoop -s feinfo command output as :
Symbol rate (min): 5.000000 MSym/s
Symbol rate (max): 45.000000 MSym/s .

therefore tuner not found some channels. how to fix it,maybe a patch for fw. anybody help me