Roomba 960 basket full light

I don’t know exactly how the sensors that are detecting if the basket is full or not, but here is what I would start with.

The first thing I would do is to try and clean both the basket and the area where you put the basket in the vacuum using a damp (not so there is dripping water, squeeze out almost all of the water) piece of paper or cloth.

The problem may be that the sensor detecting if the basket is full or not have been covered by dust or something else that makes it to think it’s full all the time.