I tried this and it didn't work. The programs list still wouldn't appear for the 33.x channels. I tried leaving all the duplicates there and then went into the EPG Guide from channel 33.1. In that case, left/right had no effect on the tv inset and 33.1's programs list remained on the screen. The 3310 EPG Guide definitely doesn't like duplicates.
I did get it fixed though. I know that 25 is slightly stronger than 19 so I positioned the antenna where it wouldn't get the strongest signal to see if I could get it to not recognize 19. That worked. I got the scan to only pick up the 25 channels.
For the record, the DISH DVR handles this by assigning a number outside the UHF range to the second set of duplicates. So 33.1/33.1 becomes 33.1/70.1. It's EPG Guide doesn't get confused.