A rating for cold ambient operation does not automatically authorise a damp or exposed electrical environment. The complete installation requirements still apply.
What the observation tells you
Condensation, water ingress and poor socket conditions create issues different from the temperature range. A freezer placed in a shed may also have restricted ventilation or unstable flooring. Covering it with a sheet to keep moisture off can obstruct airflow.
A useful next step
Check the manufacturer's conditions and arrange competent assessment of the location and supply where needed. Keep the appliance protected through a suitable installation, not improvised wrapping or electrical extensions.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.