2 Tuners not working

I just recently switched back to tivo from my cable provider as i wanted to be able to record 4 shows at once. It appears only 2 tuners are working properly and not sure where to go as i havent received any help from either end. My SNR is 34-36ish on all 4 tuners, but it seems tuners 2 and 4 are having issues, the rs uncorrected fluctuates from 18-67 million when on any channel other than the local channels. If i put all 4 tuners on local channels they work ut 1 gets very pixelated. If i tune them to anything other than local they go out and the snr fluctuates from 6-25dbs.