What the symptom can mean
An uneven load, unstable fitted position and a mechanical problem may each produce movement. The load pattern and installation history help determine which checks are appropriate.
Describe the ordinary load
Name the items and whether they were bulky, absorbent or mixed. Say when the knocking began relative to the increase in speed. Describe any movement of the cabinet or adjacent furniture separately from noise inside the drum.
Give the installation history
Tell us if the machine was recently moved, delivered or placed on different flooring. Include a visible raised floor edge, fitted door or tight counter opening when discussing an engineer's access.