Q: Recently changed rear shocks, now one side sits lower than the other and bangs going over speed bumps

With a typical spring compressor, it would be difficult to over compress the spring to the point of damaging it so that seems unlikely. Nevertheless, if no other cause is found, you may have to measure the free height of the spring and possibly test the spring. Be sure the spring is properly positioned on the spring seat of course. The only way to damage the axle beam is to improperly jack the car. If any bushing mounted suspension components were removed during the work, if such are not tightened with the full vehicle weight on the wheels, there might be some effect on height from that. What you should do is first see if the height of either side is outside the factory service manual specification. If one side is out but the other isn’t, concentrate your diagnostic efforts on the side that is out. If you want these steps performed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a vehicle is leaning diagnostic and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.