When the edge mode is set to loop, any object that is pushed through the edge with PSTN is just destroyed, not looped across. This is happening on the latest version of TPT for Windows 10 (95.0.345).
Not a bug, loop edge mode only affects the behaviour of moving particles. Particles being moved by pistons are more "teleported" than moved (i.e. they don't speed up for a tiny amount of time, arriving at their destination after slowing down).