Based on the described symptoms, it sounds like there may be a problem with misalignment and potentially worn suspension components on your 2011 Range Rover Sport HSE. Uneven tire wear on the inside of the rear tires is often a sign of a negative camber issue, where the top of the tire tilts inward. This can be caused by suspension misalignment, worn suspension components such as control arms or bushings, or even a bent frame.

The rear end fishtailing around corners and the vehicle jumping into another lane when hitting a bump could be due to the loss of stability caused by the misalignment and worn suspension components. When the rear alignment is off, it can affect the handling and traction of the vehicle, leading to unpredictable behavior like fishtailing.

It is essential to address these issues promptly to ensure safety while driving. I recommend taking your vehicle to a qualified mechanic or alignment specialist to have the suspension system inspected and realigned. They will be able to identify the underlying cause of the uneven tire wear and instability issues and recommend the necessary repairs to correct them. Regular maintenance and alignment checks are crucial to prevent premature tire wear and ensure your safety on the road.