Try to imagine which way the negative sits in the film back.. upside down, dull side to the lens. Then take another look where the light leaks are relative to the back?
Check, the dark slide baffle. Also see that the plastic face plate screws are all taught. Corners are new? Latch side is the right thickness? Door strip is the right thickness? The shell is not deformed?
I'd also try in a dark room, the bright light inside the camera trick. Inspect the sides very carefully at all angles. If light can get in, it will also come out.