Import problem (White becomes Transparent)

I have a problem. Sometimes when i import a file, white becomes transparent (monster in this case), and sometimes not. What can i do to fix this?

Example (both have 16 color palettes)


when i import this Kosmos, Everything works fine and white is white.





And when i import thisone white becomes transparent.

Why?

PS: On the Second kosmos (jumping with blade in left hand), Its not about the robot arms I added, the original one transforms white into transparent too.

X_X


EDIT* well It seems to be a stupid palette problem that is easily yet tedious to fix. But yea i can fix it, still a bit annoying. If anyone has the same problem. Import the picture into the rom, switch the transparent color from white to the one color of the 16 that is not used (there will always be one dont worry), export it again. now youll have white blocks around your sprite. Opent the pic in photoshop (or the tool you favor), select the color white and press delete. Now use paint bucket and fill all the holes in your sprite with white again and this time it will import with a correct palette. This guide sounds dumb, but anyone with the same problem will understand it.... easy yet tedious.

Cheers.