Gap between hive bodies

[Lisa]

I went out to hives today and noticed a gap between brood boxes going across the from of the hive.  Wasn't there a few days ago.  The gap is just big enough to allow them to fly in and out.

At first I thought maybe something like a skunk or mouse chewed on the edge, but there are no visible scratch or teeth marks.  No scratching in the ground in front of hive.  These brood boxes are probably 8 years old.  One is painted and the other has ecowood treatment.  The bottom ecowood box has a very slight warp on the top edge, maybe they saw light and just made the gap bigger? So weird, I've never seen this before.

This may sound lazy but can i just put some duct tape across the gap? I don't really want to swap out the boxes.

On a side note, I am not a fan of the ecowood treatment, while the color is beautiful, all the boxes i treated with it did not keep their shape.