Trailer Bounce oscillations

Is it happening when your loaded up or not loaded? The toy in the back will reduce the tongue weight. When i had a pop up the porposing was either from not enough tounge weight or the trailer toung was too high. So is it level or a little bit toung down when you tow? And thats when its loaded. If you set up un loaded and add a toy it will change stuff depending on how much weight you add. So empty may need to be a bit more toung down. Also some concreate highways can cause a vibration at certian speeds, so it kind of resonates throughout. You need to change the speed when that happens to break the cycle. Play with it a bit , you'll get it better.