Paper at the time was poor, ink would run, over time, corners of the folds would disintegrate resulting in hole/tears. Transcriptions abounded.
I spent many hours transcriping the list of 77 East Tennessee soldiers buried in the Vicksburg City Cemetery which was found in 1997. There were an extreme amount of errors. Fortunately, I had valuable diaries to work from. For instance, my ggranduncle of the 43rd Tennessee was listed as in the 48th!
George Martin