On my IG I had a few slits open up at the cove in the deep end a couple years ago. A real dog to find. Think it likewise could have been the vacuum brush maybe catching a sharp stone or something. Just a suspicion. No robotic. I usually only get fine dust or something like that in these areas so I vacuum the big stuff, bugs and the like, from the center and rigged the vacuum brush on the filter outlet to blow. I use that to kick up any dust and fine stuff into suspension then let the filter get it. Also great for blowing spots of algae which I soometimes get on the stairs and ladder rungs. With the volume of water coming out you never have to contact those areas with the brush.
Al