Depth issues (Not cutting deep enough)

Sorry in advance if this question has already been addressed. So I went to cut today for thebfirstbtime in a couple weeks. My depth seemed to be coming up a mm or more short. I even stopped the cut, changed the thickness of material and ran it again and it seemed to cut to the same depth. My z axis seems to squeal a bit. Is something maybe out of whack? Any suggestions? Thanks in advance!