When getting ready to blow open the med-bay door, Ronon uses two of his dreadlocks to tie back his hair. By the time he is sitting against the wall with Dr. Keller, his hair was tied back with a band.
In the opening scene, McKay states his diamond ring has an 18-carat diamond, but, with diamonds, carats measure size, meaning his diamond would be about the size of his thumb tip, yet we see a diamond the size of a ballpoint pen nib. He actually says eighth of a carat.