Invalid task, not in foreground

[wilmxre]

Sometimes, when you call RNLockTask.startLockTask(), you can get this error: Invalid task, not in foreground. I don't know a clear reproducible way to trigger this error yet, but i got a lot of error reportings on Sentry.

From further investigation i found out that this error is thrown in this part of the ActivityManagerService implementation
(line 8853: https://android.googlesource.com/platform/frameworks/base/+/android-5.0.2_r1/services/core/java/com/android/server/am/ActivityManagerService.java):

 void startLockTaskMode(TaskRecord task) {
  final String pkg;
  synchronized(this) {
    pkg = task.intent.getComponent().getPackageName();
  }
  boolean isSystemInitiated = Binder.getCallingUid() == Process.SYSTEM_UID;
  if (!isSystemInitiated && !isLockTaskAuthorized(pkg)) {
    final TaskRecord taskRecord = task;
    mHandler.post(new Runnable() {
      @Override
      public void run() {
        mLockToAppRequest.showLockTaskPrompt(taskRecord);
      }
    });
    return;
  }
  long ident = Binder.clearCallingIdentity();
  try {
    synchronized(this) {
      // Since we lost lock on task, make sure it is still there.
      task = mStackSupervisor.anyTaskForIdLocked(task.taskId);
      if (task != null) {
        if (!isSystemInitiated &&
          ((mFocusedActivity == null) || (task != mFocusedActivity.task))) {
          throw new IllegalArgumentException("Invalid task, not in foreground");
        }
        mStackSupervisor.setLockTaskModeLocked(task, !isSystemInitiated);
      }
    }
  } finally {
    Binder.restoreCallingIdentity(ident);
  }
}

it seems that there is no focused activity, but i am almost 100% sure the startLockTask() is called when the app is in foreground.

i submitted this ticket to raise awareness and maybe if someone has faced this issue, they might have some good insight to handle it.