I managed to open your scene, it is pretty heavy (582 mb) , @spikeyxxx is correct, it’s your irradiance volume, the size of the inner box should be only a fraction larger than the room. Yours is too large, you don’t want any probes outside the room. I would also reduce the Z probes to about 6 max, and try reducing the X and Y also, Don’t follow Kent exactly, this type of setup is hardware dependent, I used 30 probes X and Y, and I think 5 or 6 for Z.
