The answer to tough stains on vacuum is to first try manual spot cleaning with a mild detergent solution. If that doesn't work, you may need to deep clean the vacuum's filters, hoses, and interior components. Tough stains can be caused by built-up dirt, debris, and pet hair that gets trapped in the vacuum. Symptoms include reduced suction power, strange odors, and visible dirt or stains on the vacuum.
For DIY solutions, try using a vacuum cleaner brush attachment or a small amount of dish soap and warm water to gently scrub the affected areas. Allow the vacuum to fully dry before reassembling. If the stains persist or you're uncomfortable taking the vacuum apart, it's best to call a professional cleaning service to thoroughly clean and maintain your vacuum.