A panel drags or sticks
Ask about rollers, track condition and alignment. Difficulty moving does not identify a failed part by itself.
Glass looks foggy between panes
Ask about the sealed glass unit and the existing frame. Glass replacement and whole-window replacement are different scopes.
The frame or surrounding finish is damaged
Ask how the opening and water entry will be assessed. Covering damage does not establish its cause.
Agree on the scope
A symptom is a starting point. Ask what the assessment will establish and which findings would change the proposed work.
Useful references
ENERGY STAR window, door and skylight information ↗NFRC performance labels ↗General guidance. Confirm the scope for your property.