Help -- texture fails to apply on some faces, causing them to be transparent?

hi all! i’m at a bit of a loss, i’ve been searching around and i can’t figure out why this is happening. i have the following model, and when in shaded mode, it looks like this:


but when i apply the texture, some of the faces just don’t accept the texture and show up transparent:


i tried deleting and remaking the faces, moving around vertices and editing the texture… nothing seems to work! and the weirdest thing is that for some faces, the texture shows up on the inside of the face, but not the outside!

does anyone know why this could be happening, or what i could try in order to fix it? thank you in advance.