Diagnosis
The wall dock has likely become loose from the wall. The dock itself has no adjustable tightness; the issue is with the wall anchors or screws.
How to Fix It
One: Remove the vacuum and all accessories from the dock. Two: Firmly pull the dock straight off the wall. Three: Inspect the wall plugs (anchors). If they are stripped, replace them with heavier-duty drywall anchors. Four: Re-seat the dock onto the screws and press firmly until it clicks into place.
If That Didn't Work
The dock may be mounted on an uneven surface or unsuitable wall material. Remount it on a wall stud using the provided screws directly into wood, or use appropriate anchors for masonry.
Heads Up
Ensure the dock is mounted high enough that the vacuum's cleaner head does not touch the floor when docked. Contact can cause the dock to rock loose over time.