DIAGNOSIS The vacuum is not in its stable configuration for hose use. The stabilizer wheels are not deployed.
FIX 1. Ensure the vacuum is fully upright. 2. Locate the two grey stabilizer wheels at the rear base of the machine. 3. Press the button between them and pull the entire wheel assembly downward until it clicks and locks into its extended position. This creates a wider, more stable base.
IF THAT DIDN'T WORK You may be pulling the hose at too extreme an angle. When using tools, keep the main body of the vacuum directly behind you and pull the hose smoothly from the side.
HEADS UP The stabilizer wheels must be retracted (pushed up) for normal upright vacuuming and storage. They are only for hose/tool mode.