Forgot to update this. The problem was never fully figured out. After breaking down the baikals that caught fire it appeared the ones that caught fire had a lot of dust in between the capacitors on the board. Since there was no conformal coating on these boards (guess Baikal wanted to save a buck or two per board), the dust piled up and during a humid month the dust and moisture allowed for a path of conductivity. I took all my baikals apart, cleaned them and applied conformal coating. I then went back to APW3++ PSUs for the baikals. Since then, no issues. I also haven't had any other APW7 fires with any other units.