DIAGNOSIS The ice is being shaved too thin, usually because the auger blade is worn down or the mechanism's cycle time is off.
FIX The most common fix is a factory reset, which can recalibrate the cycle. Unplug the machine, wait 30 seconds, then plug it back in. Immediately press and hold the "Ice Size" button for 10 seconds until all the lights flash. This resets the internal computer. Run a cycle and see if the nuggets return to normal.
IF THAT DIDN'T WORK The problem could be water pressure/flow. If you're using the direct water line, make sure the supply valve is fully open. Low water pressure during the freeze cycle results in a thinner ice layer for the auger to scrape, creating wimpy slivers.
HEADS UP If the ice has been gradually getting smaller over many months, the stainless steel auger blade itself might be worn. It's designed to be self-sharpening, but on some units, it wears down prematurely. That's a major component replacement.