Thanks for the suggestions. I will inspect/clean the seat tube and collar to be sure it is clear of foreign matter.
I have used my Ritchey 5nM torkque key, and not even got it to the point of 5nM, so I think I am alright there, not passing the Giant 5nM spec. Unless the torque key is defective, but I have no idea how to check that. Maybe just chuck it and use something else.