From here[1], even the two a,b values seem suspicious:

k curve

  a = 0
  b = 7

r curve

  a = FFFFFFFF 00000001 00000000 00000000 00000000 FFFFFFFF FFFFFFFF FFFFFFFC
  b = 5AC635D8 AA3A93E7 B3EBBD55 769886BC 651D06B0 CC53B0F6 3BCE3C3E 27D2604B

[1]https://www.johndcook.com/blog/2018/08/21/a-tale-of-two-elli...