Here's a link to the manual for the FT 3100
If it is like the 3000 machines, the vertical alignment is done with the bed rails, and it's a fairly easy fix. There are step-by-step instructions in the manual.
If the cut is wobbly, wandering back and forth, it may be the head needs new guide rail bushings or shims in the head itself. Also in the manual.
Manuals for most all framing equipment are available in the Resources center accessed with the button in the top bar.