DIAGNOSIS The dirt tank is not fully seated or the seal is compromised. Debris is leaking from the tank-to-body interface.
FIX Empty tank. Remove it. Inspect the rubber gasket around the top of the tank. Clean it. Ensure no pet hair or debris is on the vacuum body where tank seals. Reinstall tank until you hear a distinct click on both sides.
IF THAT DIDN'T WORK The clear cyclonic chamber on the vacuum base has cracks. Inspect for hairline fractures. Chamber assembly needs replacement.
HEADS UP Carry vacuum by the handle, not the dirt tank. Lifting by tank can break latches.