First ensure that the clips or "clamps" are securely fastened. You will know by hearing two clicks when locking them down. Sometimes the second click can be tough, causing some to have an issue.
If the clamps were securely fastened and they still come unhinged, allowing water to leak out of the unit, please contact Aquascape for replacement clamps & axles. If the UltraKlean is under warranty there will be no charge for the replacements.