A light temporary film and a persistent thick mass are different observations. The distinction helps an engineer understand the pattern without relying on the vague phrase 'there is ice'.
What the observation tells you
Some refrigerator designs show droplets or brief frost on a cooling surface during normal operation. Heavy ice that obstructs food or returns unusually quickly needs a different assessment. Do not chip it away before documenting the location, and never use a sharp tool near the liner.
A useful next step
Note whether the frost changes during ordinary operation and whether food touches the area. Include a safe photograph and temperature observations rather than guessing at a sensor or refrigerant fault.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.