Photoshop CS6 Image Crop

I had this exact thing happen in CS6 and it turned out my marquee feather had been left at 2px from an earlier edit, so Image > Crop kept landing a couple of pixels inside the selection. I set Feather back to 0px in the options bar before drawing the marquee and the crop lined up exactly again. Worth double-checking yours too, since that setting sticks around until you change it.

​@Uhmazing_Grace wrote: I’ve tried redoing it a couple of times

When a tool doesn’t behave as you expect it to, the first thing to try is to reset the tool to its default options.

• Right-click the tool in the options bar (not toolbar)
• Select Reset tool

Options for tools are sticky across time and across documents until they are changed or reset.

Jane

Check the Anti-alias and Feather settings. The former will attempt to smooth the edges, the latter will increase the breadth of the soft edges - it may be that either or both are giving the impression that the cropped selection is smaller (or larger) than you’re expecting.