There are many problems and obstacles connected to the work of epigraphists. Below, I will present some of them:
1. Extremely faint letter in the texts
2. Damaged inscription, often with missing letters.
3. Linguistic problems regarding the semantics of words and differences in grammar on different stages of development of languages during which those text were created.
4. Lack of context caused by the fact that most of the texts were lost and we cannot really know exactly how many of those texts were actually created - we can know only those that we've discovered.
5. Most of the things recorded in texts are related to some significant events in history of a place due to how pricey it was to create a text in the first place. We lack crucial information regarding how regular people lived in the past.
6. Historians and Epigraphists are forced to constantly assess the statements made in inscriptions to judge whether they are true, plausible or exaggerated.
I hope it helps! :)