Looks like an error but is it really?
The term "error" is generally reserved for a mistake in printing: something out of the ordinary with the colors (missing, different, additional), the center or frame upside down, or a misspelled word, that sort of thing.
Oh ok so it's ok for there to be 3 perforated sides with one imperforated
Not really a matter or "OK" or "not OK." It's just how some stamps are designed. Coil stamps only have perforations on two opposing sides, and straight edges on the other two, for example. The example you have (first pic) was in the bottom row of the sheet when it was printed; its original companions to the left and right would've looked the same, while the stamps above it would have perforations all-around. The top row would be straight along the top edge, and the other three would have perfs.