
I think, to break this cycle, you should contain Harry overnight in a crate.
It is very unusual for a dog to soil his bed and by doing this, you are cutting out one big 'Poo oportunity'.
Following the rest of your routine and watching him like a hawk, should avoid any more accidents indoors. This will set his new pattern and hopefully solve your problem.
I do feel that no matter how many times you take him out by day, if allowed to poop indoors overnight, he will never be truly clean.
I would say that at 2 years old, and if he has a normal gut, he would only be expected to 'go' twice, maybe 3 times a day. Defaecating at night is not always because they
need to go, it is often separation anxiety or unnatural wakefulness.