how about creating a sprite/decal shadow that you make dissappear when the door opens, this problem is a typical problem with static lightmapping and what happens if you let the door model cast a dynamic shadow ?

you could also put an invisible block there to cast a shadow, however, it'll still be there when the door opens but less noticeable i guess, but you could also create a light sprite/decal to show when door opens

typically, these types of games normally avoid putting doors in areas that would create such lighting.. maybe you could alter your level/light placement a bit ?