I believe I can answer that. Essentially, that noise when the camera is moving is the product of the final gather undersampling the scene, basically it doesn’t have enough lighting information to cleanly resolve the GI.
That, combined with the visible light-leaking, temporal ghosting artifacts, and the medium setting you have it set to all make me think it’s a scalability problem. Lumen isn’t really designed to scale gracefully below high, and epic is the recommended setting for stable lighting indoors. Essentially, your settings are simply too low to resolve well. To improve this, enable hardware ray-tracing if you have the option, increase your scalability to high or epic, and increase the settings in the post-process volume under lumen to improve visuals.