gmapping message removed in rviz because its to old

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Hello everybody! I have problem with gmapping and rviz. I want to create a map of my gazebo world. Gazebo is using sim time, so I set the same for rviz. The laser scanner in rviz and gmapping say

Message removed because it is too old (frame=[laser_back], stamp=[14337.420000000])

When I pause the gazebo-simulation and press reset in rviz, the error disappears, but actually when I continue the gazebo-simulation it is the same. The time during the error message is the same as the shown ROS time in rviz and the sim time in gazebo. While running gmapping there is no tf_static (after tf static_transform_publisher). What is wrong?