Record what happens
Note the outdoor conditions, time the cycle starts, time it ends, and whether heating resumes. If the thermostat shows a defrost message, record it. A brief video from a safe location can help explain the concern without opening equipment.
Look for the pattern across several events. Is the visible frost clearing? Does the indoor temperature recover? Is this new behavior or something you have only just noticed?
Do not use an outdoor temperature reading alone as proof that the unit should not defrost. Also do not assume every change in fan sound is a confirmed defrost cycle. Ask the technician to identify the sequence if it is unclear.
Know when to request service
We would request a qualified assessment for repeated prolonged events, persistent ice, worsening room comfort, or a new fault indication. Tell the technician exactly what changed and provide the model numbers and observations.
Ask for comparison with the manufacturer's defrost sequence, including its start and stop conditions, before accepting a diagnosis. A general web article is not the timing specification for your unit.
Leave sensors, controls, refrigerant work, and service panels to the technician. Do not force defrost or bypass a control to make the unit match a generic schedule.
Avoid turning frost into damage
Carrier advises against chipping ice from the coil and calls for qualified help when ice does not clear normally. Carrier heat-pump troubleshooting.
From the ground, note obstructions or runoff near the unit and report them. Do not climb, reach into the fan area, or improvise a thawing method.
Your next action is to watch whether this cycle completes and heating returns. If the pattern is excessive or comfort is falling, request a model-specific service assessment with the observations you collected.