Originally Posted by toddnlesa
Nobody has a problem with their door rubbing the threshold?!
On occasion mine has been rubbing on the threshold. I usually go through all the screws and tighten them on the door and jamb. I keep the door closed at all times so it's supported and the chance of it drooping is less.
A stiffener plate could work but I wouldn't be surprised the door is hollow core so your plate will work if screwed to the stiles on the sides and bottom.
I think a cross door tension rod with turnbuckle might be an alternative also.