The allergen and pet filters restrict the air flow.

Again, the professional should be able to explain the cause on the invoice so you can verify it's a faulty part and not a bad renter.When the freezer works but the fridge doesn't, that's usually because something is blocking air flow from the freezer compartment.

I took a look, noted that while the AC was working, the airflow wasn't the greatest.

A few plants (hydrangeas are nice and grow well there) by the house, make sure you leave them far enough away from the house to allow them to get air flow and grow.Not sure if there is enough space to add shutters as the distance between the door and window looks tight.

You would need to have a insulation and roofing contractor come by to verify but roofs need proper insulation and airflow to deal with moisture. when two different air temps collide you will get condensation.

Chances are, the filter is just so dirty/clogged from not being replaced/cleaned that it can't get proper air flow. 

It could be anything from the unit not being the correct tonage, the property using flexible ducting that limits air flow, partially covered vents, is the property not insulated correctly, or even a fan issue. 

If the vents have low airflow and all the intakes are clear, that indicates either a filter issue or the AC coil is freezing.

As more information comes out about COVID and aerosols, I wanted to start a thread about what landlords are doing to update HVAC systems, if anything, to make sure airflow in buildings is up to par.

Normally you would also have some sort of plastic flap to ensure when this pane was removed it wouldn’t be completely open to airflow.