You can still produce a high quality shadow using the sationary light by tweaking some settings. Try increasing the resolution of the walls receiving the shadows. Something like 256 up from 64 will definitely help. Also making sure you settings are all on Epic and your Lighting Quality is set to Production. You can also reduce the shadow bias and increase the shadow sharpness. There are a lot of ways to increase shadow quality without losing performance, it’s is all about finding the appropriate balance for your project/scene.
Thanks,