Well… I tested in 4.23.
It seems like the issue is more than just the mesh… because in 4.23, here’s how it looks like (static lighting scale is at 0.1, indirect lighting quality 10, preview quality bake):
The issue is partially still there, but just making sure all the planes are correctly placed would fix the issue.I tested it with a regular static lighting scale and the issue was there, albeit much less intense than in the 4.24 version.
The baking was done with the exact same materials as in the 4.24 version, alphas included (this is just a basic lighting screenshot).
So it’s 80% 4.24, 20% planes placement. I can fix the latter, but not the first… At least I know it’ll be fixed eventually. Until then, I just have to fix the planes and hope 4.25 has this figured out.