Stop feeding and switch the appliance off. Check the documented operating arrangement before further use, including the correct baffle and the specified stopper or basket position for that model.
What the observation tells you
An overloaded chamber, an unsuitable item or a missing accessory can require different attention. Do not cover the running opening with your hand, a plate or a loose cloth to contain it. Avoid leaning over the sink to watch the mechanism.
A useful next step
With the unit safely isolated, inspect only the accessible accessories as permitted. If the correct arrangement is intact and the behaviour remains abnormal, obtain assessment rather than continuing to grind behind an improvised cover.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.