Light leaks on 4x5 negatives

[dSA]

Hello everybody,

Today was the first time ever getting back my 4x5 film developed from the lab.
Very pleased of the result at first, I started to notice some bad light leaks from both the down corners of the film.
It seems to be the same source in every negative which makes me think the problem aren't the holders but I can't explain why I'm getting this problem (the lens, the box during the trip to the lab, the camera,.... ).

Does any of you here more experienced than I am have an idea of what is going on ?

The gears used for the shoots are :
Sinar P
Schneider Kreuzach Super-Angulon 120mm F8
Kodak Portra 160

Thanks in advance for any reply,
Best regards,

Pierrick