When running a simulation or playing back a bag file with --clock, I often try to leave most of my nodes running, and only restart the thing that is publishing to /clock

Unfortunately, the tf2 internal buffer does not reset when /clock jumps backwards, and the tf2 subscribers don't have a manual mechanism to tell them that the clock has been reset, and they should clear their buffers.

See http://answers.ros.org/question/164026/how-can-i-reset-the-simulated-clock/ for more information.