We had some Tesco ones that did the same.
IIRC quite a few decades ago, the whole business of plastic bags littering the countryside was a popular topic, because they weren't breaking down. Then some chap came up with the idea of incorporating starch granules into the plastic, which would degrade in sunlight or something, and the plastic would fairly rapidly disintegrate into smaller and smaller pieces, so would no longer be visually offensive littering roadsides etc. I wonder if that process is still used, or if they have another way of getting the bags to fall to pieces.