Mike has some good advice, especially the video part.
Most people will buy/inspect their purchases based on what they burned on the last time. To this end, I invite others to report on stuff they found inadequate on their units which they may have picked up on the PDI had they checked more closely.
In our case, the bedroom door would not close or latch. The door was too tight on the hinge side and the latch was about half an inch from even reaching the hole for it. Also, the undercarriage cover became detached just under a year after we bought the unit as there was just barely enough fabric to reach. Had we checked under there, we might have seen something was amiss. Maybe, maybe not, but we did not look at the underside.
I also suggest you open and close all the windows, cabinet doors and drawers to see if they function properly. Open and close all the blinds as well. If your shower has a door, check its alignment and make sure it is not crooked as this can shear off the plastic piece at the bottom (happened to us).
There is a video on Youtube about the PDI:
(this is our daughter in the video).
There were some items wrong with our trailer that I probably would not have insisted they fix before delivery as I can do a better job myself. One was the caulking they use to secure the glass doors in some of the cabinets. So far I have replaced the caulking in three of the doors. I have also restrung three of the blinds. We have had the unit just over a year.
I don't think we would have taken delivery of the unit had we found out about the door and undercarriage ahead of time. We would have stayed until these items were corrected.