The tailstock should slide easily with the four alignment cap screws fully tightened “Step 5”.
Step 5 would have to be remedied before being able to align the tailstock. You might have to use a small mirror to look underneath to see what's binding, or use a sharpie to color the edges of the alignment plates and inside edges of the bed, slide the tailstock back and forth a few times to see where things are rubbing/binding.
Step 6 under “aligning the tailstock” states “slightly loosen the four tailstock cap screws”(item#28), and then “tap the tailstock with a wooden mallet in the appropriate direction to align the centers”.
What I get out of this is that the cap screws are still tight enough so the “alignment plates (item # 26) do not move easily , the tailstock has to be “tapped with a mallet” to move. You have to check the tailstock in three positions, with the quill fully retracted, half way then fully extended. So, the tailstock has to be able to slide and the alignment plates have to be tight enough not to shift, after the tail stock is “tapped into alignment”. I would imagine with the double morse taper the procedure would be slightly different, but the cap screws for the alignment plates would still be "slightly loosened", but tight enough so things don’t shift before you can fully tighten them.
One of the key words here is "wooden mallet", no matter how frustrating, don't get the 10 lb sledge...
Manual
https://www.teknatool.com/wp-content/uploads/2016/10/Nova-DVR-XP-manual_July-2014.pdf
