Broken line breaking in mathport output

Stream: mathlib4

[Ruben Van de Velde]

https://github.com/leanprover-community/mathlib3port/commit/6797a637bad89c884a1ea52371e5256b851945f5 improved output in a lot of places, but it also started using syntax like

@[ext]
theorem cokernel_π_imageSubobject_ext {L M N : ModuleCat.{v} R} (f : L ⟶ M) [HasImage f]
    (g : (imageSubobject f : ModuleCat.{v} R) ⟶ N) [HasCokernel g] {x y : N} (l : L)
    (w : x = y + g (factorThruImageSubobject f l)) : cokernel.π g x = cokernel.π g y := by subst w;
  simp

which doesn't work. Not sure what caused this or who should look at it