a couple of things I have observed since having our Samsung Series 5 (2020) WW90T534DAW washing machine with auto dosing when detergent is running low but not quite run out (not run out enough to flash up the "detergent low" message on the display)
1.) the pump gets really noisy at that stage with a louder "glug glug noise" 2.) there does not seem to be as many bubbles in the drum at this stage
Not faults as such, but this just seems to bee the way it is - once compartments filled up again then no problems , works as it should and the pumps are not as noisy.