Rocking can be caused by unstable flooring, poorly adjusted leveling feet or loose frame bolts. Push down on diagonally opposing sides of the elliptical to check leveling feet for unevenness. Adjust the leveling feet if you can rock the elliptical.
Check all frame bolts for looseness and tighten any loose frame bolts. Periodically check frame bolts and tighten any loose bolts when performing routine elliptical maintenance. If the frame bolts are tight and the leveling feet are all firmly against the floor to prevent rocking, then check the stability of flooring under the elliptical. Using your foot, press down firmly on the frame above each leveling leg to check for rocking. If the elliptical rocks, move the elliptical to an area with stable flooring.
These repairs may help solve your elliptical machine problem
Perform elliptical maintenance
Inspect and tighten all parts of the elliptical regularly. Replace any worn parts immediately. Lubricate all moving parts using all-purpose grease. Replace the battery if it's weak or dead.