Pipes was my initial thought as well, but it just doesn’t look right at all… plus they don’t seem to be centered on the block grid.
My next thought was … The Dreaded Block Parasite …but it doesn’t quite look like that either (and I wasn’t expecting to see that in game just yet!).
May be one for the devs to take a look at … unless anyone else has experienced this before. Devs are on UK time, so you may get a reply tonight if any of them pop onto the forums, but failing that, it may be tomorrow morning before you hear back.