For maximum performance, It is important that the load is evenly balanced inside the drum before the machine starts the spin section of the cycle. This will prevent the machine from excessive vibration and movement. Your machine has a safety sensor built in which carefully distributes the clothes around the surface of the drum to give the quietest spin possible. So on some occasions the machine may not spin.
So how does the sensor work?
It will carefully sort the washing around the drum before it spins
Can the sensor stop my machine from spinning the load?
Yes it may do. If there is just one item in the drum, a hooded jumper or a bath robe for example then it will not be able to distribute the load evenly around the drum. It discovers the load is unbalanced and stops the machine from spinning that particular load. A very small load can also be detected by the sensor and again it simply will end the cycle without spinning dry.