The reason for this is because at least one of the raster layers in the Table of Contents (TOC) is displaying the raster resolution values. This is a current issue in ArcGIS that results in the data frame not aligning properly.
To remedy this situation, right-click the raster layer in the Table of Contents and click Properties
. Navigate to the Display tab in the Layer Properties dialog and uncheck the Display raster resolution in the table of contents option.