Some weird stuff going on.

ContainerTransformWeirdness.kt

@Preview
@Composable
fun ContainerTransformWeirdness() {
  var scene by remember { mutableStateOf(Scene.Grid) }

  SharedTransitionLayout(modifier = Modifier.fillMaxSize()) {
    AnimatedContent(
      targetState = scene,
      transitionSpec = {
        fadeIn() togetherWith fadeOut()
      },
      label = "Screen Transition"
    ) { target ->
      when (target) {
        Scene.Grid -> {
          Column(
            modifier = Modifier
              .fillMaxSize()
              .windowInsetsPadding(WindowInsets.statusBars)
              .padding(8.dp),
            verticalArrangement = Arrangement.spacedBy(8.dp)
          ) {
            FakeSearchBar(
              modifier = Modifier
                .fillMaxWidth()
                .height(60.dp)
            )
            LazyVerticalGrid(
              modifier = Modifier.fillMaxSize(),
              columns = GridCells.Fixed(2)
            ) {
              item {
                Column(
                  modifier = Modifier
                    .sharedBounds(
                      sharedContentState = rememberSharedContentState(key = "container"),
                      animatedVisibilityScope = this@AnimatedContent,
                      enter = fadeIn(),
                      exit = fadeOut()
                    )
                    .fillMaxWidth()
                    .height(300.dp)
                    .clip(RoundedCornerShape(16.dp))
                    .background(color = Purple80)
                    .clickable {
                      scene = scene.toggle()
                    }
                ) {
                  Box(
                    modifier = Modifier
                      .sharedElement(
                        state = rememberSharedContentState(key = "element"),
                        animatedVisibilityScope = this@AnimatedContent
                      )
                      .fillMaxWidth()
                      .height(200.dp)
                      .clip(RoundedCornerShape(16.dp))
                      .background(color = Purple40)
                  )
                }
              }
            }
          }
        }

        Scene.Closeup -> {
          BackHandler {
            scene = scene.toggle()
          }

          Column(
            modifier = Modifier
              .sharedBounds(
                sharedContentState = rememberSharedContentState(key = "container"),
                animatedVisibilityScope = this@AnimatedContent,
                enter = fadeIn(),
                exit = fadeOut()
              )
              .fillMaxSize()
              .clip(RoundedCornerShape(16.dp))
              .background(color = Purple80)
              .padding(8.dp),
            verticalArrangement = Arrangement.spacedBy(8.dp)
          ) {
            Box(
              modifier = Modifier
                .sharedElement(
                  state = rememberSharedContentState(key = "element"),
                  animatedVisibilityScope = this@AnimatedContent
                )
                .fillMaxWidth()
                .height(200.dp)
                .clip(RoundedCornerShape(16.dp))
                .background(color = Purple40)
            )
            Column(
              modifier = Modifier
                .fillMaxSize()
                .clip(RoundedCornerShape(16.dp))
                .background(color = Color.White)
            ) {

            }
          }
        }
      }
    }
  }
}