My first floor air/heating equipment is in a crawl space and being somewhat physically handicapped I can't get in there any longer. I discovered that the return duct register box and duct have become separated as shown in this photo. Is it ok to I seal this from the inside with mastic and aluminum tape or does it have to be resealed around the outer rim of this box? I am getting ready to sell the house so I don't want this to be an issue with the home inspector.
Taken looking downwards, although not shown, there are a couple of small holes in the black material to the left