Welcome to the forums.
This could be caused by many things.
The first that springs to mind is that your document could be low-DPI and moving the layer could make the pixels in the layer non-aligned with the pixels of the document. When this happens the software will try to ‘fill-in’ the pixels as best it can and therefore the layer could look ‘fuzzy’.
My attached video shows a simple example. Note how things change when I set “Force Pixel Alignment” OFF and ON.
Can you check to see if this is the problem?
2020-08-16 10-01-38.mp4
