Only use a combination and stacking arrangement approved for the appliances. Similar width or a flat washer top does not establish safe support.
Understanding this situation
Movement, fixings, access and load-bearing requirements matter. An improvised shelf or non-matching kit can create a hazard even if the appliances seem stable when switched off.
A useful next step
Use competent installation advice and the correct model information. Do not climb on, lean heavily against or unstack the arrangement alone for cleaning. Tell the repair team about the stack before a visit so safe access can be planned.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.