Memory leak when swizzling CAMetalLayer.nextDrawable?

I am swizzling CAMetalLayer.nextDrawable using the code provided on StackOverflow in this answer so I can save the textures from each drawable.

@objc func newNextDrawable() -> CAMetalDrawable? {
     // After swizzling, originalNextDrawable() actually calls the real nextDrawable()
     let drawable = originalNextDrawable()

      // Save the drawable
      nextDrawableExtPropertyData._currentSceneDrawable = drawable

      return drawable
 }

However, when running in Instruments, this code is spawning a bunch of leaks involving CAMetalDrawable and NSMutableArray (I think the drawables are referencing arrays). I don't see these same leaks if I don't swizzle.

Anyone know why this would be leaking?

Thanks.