rviz2: Message Filter dropping message [closed]

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Hello,

I have the following problem. I get a speed vector from a subscriber. As a first step I want to create a line in rviz which moves according to the speed vector.

As soon as I start rviz2 and set the right topic I get the following output on the terminal: INFO] [rviz]: Message Filter dropping message: frame 'line_ID' at time 1607353081.030 for reason 'Unknown'.

tracking_node.cpp

subscriber_callback

private:

void tracking_linear_vel_callback(sensor_msgs::msg::Imu::SharedPtr msg)
{
  //vec_vel_struct linear_vel;

  linear_vel_.at(0) = msg->linear_acceleration.x;
  linear_vel_.at(1) = msg->linear_acceleration.y;
  linear_vel_.at(2) = msg->linear_acceleration.z;

  // get lines for rviz
  lines_ = obj_Print_rviz.init_linear_vel(linear_vel_);
  lines_.header.stamp = this->now();
  //publish rviz lines
  rviz_pub->publish(lines_);
}

setup_rviz

 #include "print_to_rviz.h"
 using namespace print_to_rviz;

 PrintToRviz::PrintToRviz()
 {

line_strips.header.frame_id = "line_ID";  
line_strips.ns = "lines";
line_strips.action = visualization_msgs::msg::Marker::ADD;
line_strips.pose.orientation.w = 1.0;

line_strips.id = 0;

line_strips.type = visualization_msgs::msg::Marker::LINE_STRIP;

//sacling
line_strips.scale.x = 2;
//color
line_strips.color.a = 1.0;
line_strips.color.b = 1.0;
}

 PrintToRviz::~PrintToRviz()
 {
 }
 visualization_msgs::msg::Marker PrintToRviz::init_linear_vel(std::array<double, 3> linear_vel)
 {

  line_strips.points.clear();
  // create vertecs
  points.x = linear_vel.at(0);
  points.y = linear_vel.at(1);
  points.z = linear_vel.at(2);
  // push points into line strip
  line_strips.points.push_back(points);

 //  std::cout <<"x: " << linear_vel.at(0)<<"\n"<< "\n";
 //  std::cout <<"y: " << linear_vel.at(1)<<"\n"<< "\n";
 //  std::cout <<"z: " << linear_vel.at(2)<<"\n"<< "\n";

return line_strips;
}

I have now expected that every time the Subscriber_Callback is called a new line is written to rviz2 instead of the speed vector. What exactly am I doing wrong? Many thanks for the help in advance!