Component used: Navigation
Version used: 1.0.0-alpha11
Devices/Android versions reproduced on: irrelevant

I have a fragment like this:

<fragment
android:id="@+id/teamDetailFragment"
android:name="com.optima_apps.fkcz.ui.team.teamdetail.TeamDetailFragment"
android:label="{player_name}" <== PARAMETRIZED LABEL (from a plain string argument)
tools:layout="@layout/fragment_team_detail">
<argument
android:name="player"
app:argType="com.optima_apps.fkcz.models.Player" /> <== CUSTOM CLASS ARG TYPE
<argument
android:name="player_name"
app:argType="string" />
</fragment>

When parametrized label is used in combination with custom class argument type on a fragment, the app crashes when activity is recreated with a saved instance state. To reproduce, have a fragment configured as shown above, then in Developer Options enable "Don't keep activites" to force activity to destroy as soon as you leave it, then return to activity and it should crash like below:

2019-02-05 12:57:22.012 5790-5790/com.optima_apps.fkcz E/Parcel: Class not found when unmarshalling: com.optima_apps.fkcz.models.Player
java.lang.ClassNotFoundException: com.optima_apps.fkcz.models.Player
at java.lang.Class.classForName(Native Method)
at java.lang.Class.forName(Class.java:400)
at android.os.Parcel.readParcelableCreator(Parcel.java:2489)
at android.os.Parcel.readParcelable(Parcel.java:2443)
at android.os.Parcel.readValue(Parcel.java:2346)
at android.os.Parcel.readArrayMapInternal(Parcel.java:2698)
at android.os.BaseBundle.unparcel(BaseBundle.java:269)
at android.os.BaseBundle.containsKey(BaseBundle.java:345)
at androidx.navigation.ui.AbstractAppBarOnDestinationChangedListener.onDestinationChanged(AbstractAppBarOnDestinationChangedListener.java:90)
at androidx.navigation.ui.ToolbarOnDestinationChangedListener.onDestinationChanged(ToolbarOnDestinationChangedListener.java:57)
at androidx.navigation.NavController.addOnDestinationChangedListener(NavController.java:218)
at androidx.navigation.ui.NavigationUI.setupWithNavController(NavigationUI.java:292)
at androidx.navigation.ui.NavigationUI.setupWithNavController(NavigationUI.java:241)
at com.optima_apps.fkcz.FKCZActivity.onCreate(FKCZActivity.kt:41)
at android.app.Activity.performCreate(Activity.java:6915)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2746)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2864)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1567)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:156)
at android.app.ActivityThread.main(ActivityThread.java:6523)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:942)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:832)
Caused by: java.lang.ClassNotFoundException: com.optima_apps.fkcz.models.Player
at java.lang.Class.classForName(Native Method)
at java.lang.BootClassLoader.findClass(ClassLoader.java:1346)
at java.lang.BootClassLoader.loadClass(ClassLoader.java:1406)
at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
at java.lang.Class.classForName(Native Method)
at java.lang.Class.forName(Class.java:400)
at android.os.Parcel.readParcelableCreator(Parcel.java:2489)
at android.os.Parcel.readParcelable(Parcel.java:2443)
at android.os.Parcel.readValue(Parcel.java:2346)
at android.os.Parcel.readArrayMapInternal(Parcel.java:2698)
at android.os.BaseBundle.unparcel(BaseBundle.java:269)
at android.os.BaseBundle.containsKey(BaseBundle.java:345)
at androidx.navigation.ui.AbstractAppBarOnDestinationChangedListener.onDestinationChanged(AbstractAppBarOnDestinationChangedListener.java:90)
at androidx.navigation.ui.ToolbarOnDestinationChangedListener.onDestinationChanged(ToolbarOnDestinationChangedListener.java:57)
at androidx.navigation.NavController.addOnDestinationChangedListener(NavController.java:218)
at androidx.navigation.ui.NavigationUI.setupWithNavController(NavigationUI.java:292)
at androidx.navigation.ui.NavigationUI.setupWithNavController(NavigationUI.java:241)
at com.optima_apps.fkcz.FKCZActivity.onCreate(FKCZActivity.kt:41)
at android.app.Activity.performCreate(Activity.java:6915)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2746)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2864)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1567)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:156)
at android.app.ActivityThread.main(ActivityThread.java:6523)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:942)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:832)
Caused by: java.lang.NoClassDefFoundError: Class not found using the boot class loader; no stack trace available

I have already Googled this a bit and this could be the solution: https://stackoverflow.com/a/18126250/4695418

When I change the label to be a static string, the library never goes into part of code that's crashing, and everything works properly, so I'm sure the issue is not on my side.

If you need any additional info I'm here.