The model House (Large, Abandoned) [Land_u_House_Big_01_V1_F] has at least one window that does not let grenades pass through. This "window" is simply a cut out in the wall and has no grill or anything obstructing it. Bullets can be fired through, however grenades, chemlights, etc. bounce back as if they're hitting a wall.
This window is located on above the back entrance.
UPDATE: ALL windows in this model block grenades.
Place the building "House (Large, Abandoned)" via the Eden editor in an empty map, or find the house on Altis/Stratis/Malden (see image for an example location).
Chuck a grenade at this window.
See video:
https://youtu.be/Sc2vk6FbJLM
I haven't tested all the windows, but the dev team should check it out. Neither have I tested ALL other buildings, but the other abandoned house models do not appear to have this issue.
UPDATE: All windows in this model have this problem.
do u see the window frame between the bugwindow and the door a bit to the left(first 10sec of the video)? i can clearly see a ambient shadow on the wall. looks like the frame is just a bit off on this model.
The model shown in the video is u_house_big_01_v1_f.p3d, and the same issue also exists with u_shop_01_v1_f.p3d. Both of these models are missing openings for the windows in their geometry LOD.