There can be many issues that a Data Analyst might face when working with data. Here are some of them:
The accuracy of the model in development will be low if there are multiple entries of the same entity and errors concerning spellings and incorrect data.
If the source the data being ingested from is not a verified source, then the data might require a lot of cleaning and preprocess before beginning the analysis.
The same goes for when extracting data from multiple sources and merging them for use.
The analysis will take a backstep if the data obtained is incomplete or inaccurate.