DIAGNOSIS The main suction channel is partially blocked. Debris gets past the main brush but gets stuck before reaching the dustbin, creating a clog that reduces airflow and cleaning power.
FIX Empty the dustbin. Now, look into the circular suction intake hole inside the robot where the main brush sits. Use a long, thin object (like a chopstick or the tool that came with it) to gently poke and clear any compacted dust or debris lodged deep in that channel. Also, check the rubber seal around the dustbin door for clumps of hair.
IF THAT DIDN'T WORK The filter might be completely saturated. Remove the HEPA filter from the dustbin and tap it firmly against a trash can to dislodge fine dust. For a real fix, rinse it with water (only the filter, not the dustbin) and let it dry COMPLETELY for 24 hours before reinstalling.
HEADS UP This clogging happens faster if you vacuum fine plaster or construction dust. For that kind of mess, you're better off with an upright vac first.