Hi,
If the warning happens only 1 or 2 times at the beginning, it is not the problem. With your commands, rtabmap is launched in rtabmap namespace while rtabmapviz isn't. To make all services and topics correctly connected to rtabmap node, they should be both in the same namespace. When launching rtabmapviz, try:
export ROS_NAMESPACE=rtabmap
rosrun rtabmap_ros rtabmapviz _subscribe_odom_info:=false _frame_id:=camera_link