I tried this:
Reducing your min lightmap resolution, while also increasing your actual lightmap resolution.
Min Lightmap Resolution is used to determine how much padding will be placed around the lightmap UV islands when Unreal generates the lightmap UVs, if you set it too high then you’ll get texel bleed from the adjacent islands, this is mainly noticeable at lower mips. In general you want it to be quite a bit lower than your actual lightmap res.
16 is probably way too low for min res, I wouldn’t go below 64. I would expect 64 min with a 512 lightmap to produce the same results. The minimum resolution is basically a balancing act, you want it to be as low as you can get it while still getting good results, but you don’t want it to be too low or you’ll be wasting too much of your texture space on padding.
• Changing to different light sources as well as changing the movability of the light sources (Static, Stationary, Moveable): Changing lights to Moveable does improve it a lot but it also means I won’t be able to have that many lights in the scene close together.
• Reduce the smoothing done by lightmass in WorldSettings->Lightmass->IndirectLightingSmoothness. A value of .6 or so can work well. You might also need to jack up the IndirectLightingQuality to 2 or so to compensate for this.
Combine separate meshes in 1
But that didn’t help