TVFool shows strong reception (+26 NM) for channel 51 in your area even though it is a low powered ("-LD") station. However if for some reason you would need an amplifier, I would recommend the RCA TVPRAMP1Z preamp which is quite overload resistant (since you have strong +60 NM stations). It has been tested at a variety of forums in conditions of mixed weak and strong RF signals and does not readily overload a tuner. Lowes carries them for $30 which means you could pick one up, test for your situation and see whether a preamp applies to your problem (if not return it within 30 days).
If you need a channel specific preamp (no amplification except for 51), try Jan Jenca who makes channel specific preamps. You tell him that you need a channel 51 specific preamp just to boost up that channel\frequency. I’ve used Jenca for just such circumstances.
If however it is not a signal strength issue but as Smurph indicated possibly a PSIP issue, do what a friend of mine did. He got a “channel specific” DVR just for one channel that his Tablo was having issues with - a Homeworx 180. He absolutely wanted to be able to record this specific channel and was willing to have 2 DVRs - one (Tablo) for all the channels minus one; another DVR for the Tablo problematic channel (with which the 180 seems not to have metadata issues). Several people have used the Homeworx as a backup to their Tablo including me (check the various forum threads about that). MarkKindle uses his just for recording sports events. The 180 goes for the ridiculously low price of $30 so it also could be a cost effective solution (of sorts)!