Clean cabin filter rules out the most obvious airflow restriction cause. Expansion valve stuck open or a faulty evaporator temperature sensor are the two most likely culprits for the freeze and thaw cycle you are describing.

Over 60 photos including underbody shots on a lift and a full scan printout is the standard every inspection should meet. Anything less and you are paying for someone's opinion rather than actual documented evidence.

Subtle jerkiness in slow traffic on a car that was previously buttery smooth is exactly the kind of early symptom worth catching before it develops into something more serious. Good instinct not to ignore it.