With the rental boxes.. it can be a roll of the dice.. they all come from one pool... can get a good almost new or a rough one (though they should be weeding out the BAD ones)
As for the other issues... did you just put in the box yourself? Or did you ever get a tech out.
If not.. that would be your first thing likely. Not that you did anything wrong... just usually MOST of those issues, are SIGNAL related. Its possible that the signal just to that spot, isnt very good. The techs should be able to tweek things, replace splitters, connectors, etc as needed to get it more up to snuff.