I think there's a few things to be distinguished here.
Are we just talking about solving problems without active thinking? That was the original question ("Is it possible to solve problems without active thinking?")
Are we talking about solving problems SPECIFICALLY in a dream- where the idea for a solution appears to you in a hallucination during sleep?
Are we talking about hallucinations during sleep being a general indicator of the brain "refactoring" and integrating skills and knowledge?