I think you are missing an actual toolbar inside the collapsing toolbar.
try adding a toolbar after the linear layout’s closing tag.
example:

<androidx.appcompat.widget.Toolbar
    android_id="@+id/toolbar"
    android_layout_width="match_parent"
    android_layout_height="?attr/actionBarSize"
    android_background="@color/colorPrimaryLight"
    android_theme="@style/ThemeOverlay.MaterialComponents.Dark.ActionBar"
    app_layout_collapseMode="pin"
    app_title="Toolbar title" />

and another thing I noticed, you AppBarLayout has android:fitsSystemWindows="true" so check that as well.

I have the following layout that has a collapsing toolbar with a LinearLayout inside –

<?xml version="1.0" encoding="utf-8"?>

<layout xmlns_android="http://schemas.android.com/apk/res/android"
    xmlns_app="http://schemas.android.com/apk/res-auto"
    xmlns_tools="http://schemas.android.com/tools">

    <androidx.coordinatorlayout.widget.CoordinatorLayout
        android_layout_width="match_parent"
        android_layout_height="match_parent"
        android_orientation="vertical"
        tools_context=".application_flow.group.GroupOverviewFragment">

        <com.google.android.material.appbar.AppBarLayout
            android_layout_width="match_parent"
            android_layout_height="200dp"
            android_elevation="10dp"
            android_fitsSystemWindows="true"
            android_stateListAnimator="@animator/show_toolbar">

            <com.google.android.material.appbar.CollapsingToolbarLayout
                android_layout_width="match_parent"
                android_layout_height="match_parent"
                app_collapsedTitleGravity="center"
                app_contentScrim="@color/colorPrimary"
                app_expandedTitleGravity="top"
                app_layout_scrollFlags="scroll|exitUntilCollapsed"
                app_title="Lohamei Galipoly 38"
                app_titleEnabled="false"
                app_toolbarId="@id/group_tasks_toolbar">

                <LinearLayout
                    android_layout_width="match_parent"
                    android_layout_height="match_parent"
                    android_layout_marginStart="14dp"
                    android_layout_marginEnd="14dp"
                    android_orientation="vertical"
                    app_layout_collapseMode="parallax"
                    app_layout_collapseParallaxMultiplier="0.6">

                    <androidx.appcompat.widget.Toolbar
                        android_id="@+id/group_tasks_toolbar"
                        android_layout_width="match_parent"
                        android_layout_height="?attr/actionBarSize"
                        app_contentInsetStartWithNavigation="0dp"
                        app_layout_collapseMode="pin"
                        app_navigationIcon="@drawable/left_arrow_white"
                        app_titleTextColor="@color/white" />

                    <Space
                        android_layout_width="match_parent"
                        android_layout_height="0dp"
                        android_layout_weight="1" />

                    <TextView
                        android_layout_width="wrap_content"
                        android_layout_height="wrap_content"
                        android_layout_gravity="center"
                        android_layout_marginBottom="30dp"
                        android_textColor="@color/white"
                        android_textSize="18sp"
                        tools_text="Total group tasks: 8" />

                    <com.google.android.material.tabs.TabLayout
                        android_id="@+id/group_tasks_tab_layout"
                        android_layout_width="match_parent"
                        android_layout_height="wrap_content"
                        app_tabIndicatorColor="@color/white"
                        app_tabMode="fixed"
                        app_tabSelectedTextColor="@color/white" />

                </LinearLayout>

            </com.google.android.material.appbar.CollapsingToolbarLayout>


        </com.google.android.material.appbar.AppBarLayout>

        <androidx.viewpager2.widget.ViewPager2
            android_id="@+id/group_tasks_viewpager"
            android_layout_width="match_parent"
            android_layout_height="wrap_content"
            app_layout_behavior="com.google.android.material.appbar.AppBarLayout$ScrollingViewBehavior" />


    </androidx.coordinatorlayout.widget.CoordinatorLayout>

</layout>

For some reason it does not collapse the entire content of the LinearLayout like it should and it is being left fixed in place.

This error seemed to start happening after I switched to work with the LinearLayout inside my CollapsingToolbarLayout

What is it that I am missing?