When he does have an accident, are you scolding at all? Scolding doesn't mean you have to yell or rub their nose in the mess. You can still go "NOO! OUTSIDE!" And clap your hands or something to distract him. When you do catch him going outside successfuly, praise like your puppy just won you the lottery. I am sure you are doing this already though

You are doing a lot of very good things and keep it up! I am having potty training ups and downs withy my 10 month old. She was tough to break at first because she had a UTI that I didn't have her tested for until 5 or 6 months of age - after medication I thought she was potty trained! Nope. I later found out that she was resoiling over old spots, behind the couch. Since then I have gated off her access to the areas she has accidents in.

If he is still having pretty frequent accidents, then I would go ahead and reduce his amount of den space.

I think Karlin is right, a lot of it is just that potty training happens as they get older and as long as we are very patient and consistent with them.