If you place the end crystals down to create a new enderdragon, the portals in the end disappear, but when you stand on the place where the end portals should have been and break one of these crystals you're game starts to lag so badly that it almost crashes, then you'll be teleported to the overworld but when you walk back to the portal in the overworld the portal is missing 3 endereye's (also I did make the portal in creative because I did not wanted to search the original one because that takes time, and no. I did not remove these eye's myself..)