does this also happen at runtime? like in PIE (the play button at the top)
does it stop with more lights? (this shouldn’t be the case, though it could in some situations it can be)
if you move the lights closer to the walls or the walls closer to the lights, does that make it less pronounced or goes away.
you might be running against a max calculations of light bounces. To keep performance “reasonable” while navigating in the editor the engine will reduce the number on maximums for things. When you hit PIE the window of the game at that time has many of these “restrictions” removed or softened, because it is supposed to be more clearly matching what the engine will be doing after a build.
there are still things that are kind of limited in the Editor that will not be limited in a full build (even Development build); these limits are usually safeguards that are trying to avoid a catastrophic crash.
if this still happens during PIE/build, or after manually forcing the lighting to build you may need to look into a few things:
- this could be hardware related where your graphics card or APU physically cannot do the calculations either in the form of raw compute or like VRAM; meaning you may have a hardware target situation, and maybe a legitimate “minimum/suggested specifications” for the point of release.
- reduce the number of lights in the scene. (this is probably not what you want to hear but one of those “if it hurts don’t do it” kind of thing)
- adjust the distance of the lights. in the properties of the light itself where these reflections the primary contributor is distance of the light ray.
- maybe add an invisible light in that corner to produce a desired shadow though this can create some “anomalies” with moving objects (kind of like the nail polish to cover up a paint chip/scratch)
- adjust the “number of bounces” in the Post-Processing volume to clean this up
- the most direct answer is to look into “baked lighting” instead of dynamic shadows though this will have many of the negative effects of “baked lighting” namely needing to re-bake every time you change the scene/level, and other things dealing with level streaming.