Each opening changes the cavity conditions, and repeated basting can make the actual cooking sequence differ from the recipe's assumed one. The displayed target is not a continuous measurement of food temperature.
What the observation means
A large roasting dish may need the door open for longer than a quick visual check. Steam and hot air escape, and the appliance then works to recover its selected conditions. This does not prove that every long roast is a usage issue, but it is relevant when comparing an unusually interrupted meal with a previous undisturbed one.
A useful next step
Use the recipe's checking schedule and the oven's safe handling guidance. Record prolonged openings if food now takes longer. Do not keep the door open while the oven runs to assess heat by touch. A significant change during ordinary use still deserves a clear model-and-mode enquiry.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.