My staples shedder SPL-1506X stopped shredding any ideas how to fix it

SOURCE: Automatic switch does not shut off after shredding

These shredders have a "paper in" sensor. This is either optical or mechanical.
Sounds like the sensor is blocked and therefore "thinks" there is still more paper left, and this is why it keeps going.

Before you do anything UNPLUG THE SHREDDER.
The sensor is located about in the middle and at the level of the blades.
If it's mechanical, you should see a little finger, else it is electronic.
Shine a light in the area and you should be able to spot where the blockage is.
A shot with compressed ais usually gets rid of the offending particles.

After you're finished working on it, set it back securely on the basket and plug it in.