As those vinyl liners tend to fade and discolor with the harsh chemicals causing them to be replaced fairly often to maintain a best appearance.

Pay attention to smelly or discolored trim too, particularly around windows that they may have smoked near.

The inspector recommended I get a licensed HVAC engineer to check it.Other things are ---Open mortar joists/loose spalled brick at the chimney, loose shingles on dormer---Several windows painted shut sash cords missing, non-operable, rear deadbolt "keyed only" should have thumb turn for emergency egressloose/ flaking paint, possible lead-based paint---Cracked concrete at entry porch,--missing guard rail at rear steps,--several downspouts missing splash blocks/draining too close to the house---Grading is flat to sloping toward foundation additional top soil/grade modification may be needed---Suggested GFCI protected outlets at all wet locations as a safety improvement---Discoloration on floor joists in the basement, have evaluated for cleaning, possible treatment---Garage needs to be repaired completely.

Could be close to the end of its life, hail damage, discoloration, missing shingles, wind damage, etc.

Mine don’t have discoloration.  

I technically agree with that as single-spot repair isn't 100% and there will be discoloration.

Would you say this is something that could be fixed? I have no idea..

Analyzing a single-family home & the numbers look great, BUT it looks like it's a smoker's home from the photos (discoloration around vents and ceilings).

They accomplished this by painting large, discolored squares in multiple areas, of every wall, of every room (with only a couple exceptions).

There are signs posted in the house on same wall of all three floors saying "this area has been treated for surface discoloration, it has not undergone sub-surface inspection" it is even posted on a concrete wall in the basement.