Yeah, this one's common. It's almost always a blockage. Something is caught in the fan or the air inlet.
First, unplug the appliance from the mains. Never clean it while it's plugged in.
- Look for blockages in the air inlet holes on the filter shrouds.
- Check the small aperture inside the loop amplifier.
- Use a soft brush to remove any dust and debris from those areas.
If that didn't work, the filters might be the issue. If the filters haven't been changed when prompted, or if the unit was run without filters, internal blockages can occur. You'll need to remove the filter shrouds and check the air inlet holes under the filters.
Heads up: Never spray perfumes, air fresheners, or essential oils near the filter or the appliance. That gunk can cause problems.