I’ve found that the best way to handle this is to separate the window geometry into its own mesh and disable “Affects Distance Field Lighting” or as you discovered, set the distance field resolution to 0 to disable distance fields for the window mesh entirely.
This ensures you still get proper indirect lighting from the main wall, and only the window geometry is ignored (it will still be picked up by screen traces, which typically looks fine)
This is only an issue in software raytracing, as the rays have to traverse the global distance field which is really low resolution.