Treat discolouration, melting or a burning smell as a reason to stop use and obtain qualified help. Do not keep operating the appliance simply to see whether the mark grows.
What the observation tells you
The source may involve the plug, socket, connection or appliance load, and it cannot be established safely from appearance alone. Moving the plug to another socket may transfer the risk rather than solve it. Avoid touching hot or damaged electrical fittings.
A useful next step
Arrange safe isolation and suitable alternative food storage. Describe the visible signs and any tripping, without conducting further powered tests. The supply and appliance may both need assessment.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.