The most likely culprits are:
1) If it is over 16 months old by production date, it may have the stainless steel shaft which could break, we now use a titanium alloy, send the pump in, it will be replaced under warranty.
2) If it is a newer pump, the drive unit may be cemented to the shaft by calcium, or fine sand or debris. Gently pull out the drive unit with a twisting motion and clean the shaft with vinegar and a small brush and clean the hole in the drive unit with a pipe cleaner or small brush.