Cleaning ducts

Hello, I want to remove a stubborn odor from my bedroom vent. I hired a duct-cleaning company to vacuum out my ducts, but the smell is still there. The company used a portable vacuum system and a rotor brush which they inserted into each vent. I asked if they cleaned out the entire duct system or just the part close to the vents. He told me the entire system. Now I am suspicious of that.

I called another duct-cleaning company who says they use a truck-mounted vacuum system which is more powerful than the portable one. I believe the source of the smell is deep inside my duct system. Is there any company that cleans out the entire duct system, and is the truck-mounted vacuum system more effective?