I was playing on my hardcore world when I was making a tower of white concrete powder to convert to concrete when I got to a chunk border and placed the concrete powder on the wall that was on the chunk border, it would cause my frames to drop from around 240 to 45 fps, this would only happen after a few blocks were already falling (around 3-5) and I tested it later with all the gravity affected blocks and it did the same thing. All other areas are able to handle it except on a chunk border.