The version update system was broken for earlier version, recommend you install directly:
Changes in version 5.5.9
• Fixed regressions in non-Retina display Macs after adding Retina display support.
Changes in version 5.5.7
• Unlimited length Audio Quick Looks, no longer bound by the 60 minute limit.
• All new Audio Quick Look generation engine. More stable and dynamic.
• Sample Tool behavior change. When a slice marker and a loop are on top of each other the loop will move first via the mouse.
• Switched to single clicking folders in the sound list due to popular user unrest!