DIAGNOSIS The ice level sensor arm is either stuck, misaligned, or the ice itself is piling up in a way that prematurely triggers it.
FIX Empty the basket completely. Look at the sensor arm inside the basket slot—it's a small plastic paddle. Manually move it up and down its full range. It should move freely and spring back up. If it's sticky, clean it with a Q-tip dipped in vinegar to dissolve any scale. Also, check that the basket itself is perfectly seated; if it's tilted, the arm can't move correctly.
IF THAT DIDN'T WORK The shape of the ice can cause this. If the cubes are small or misshapen, they can fall and stack directly under the sensor arm instead of spreading out. Try changing the cube size setting (if your model has it) to 'Large'. The bigger, more uniform cubes tend to stack more predictably.
HEADS UP The sensor isn't measuring weight, just physical obstruction. A single cube landing perfectly upright under the arm can trick it. Giving the basket a light shake after a cycle often settles the ice and frees the arm.