Level 10 Ground Zero
I've checked every corner of the map and destroyed every enemy of the map, but I can't achieve the extra mission of this level and find the Gwen crate, so I manager to open SEA_FACT01_M10.LUA and find that the spaceship crate seems to be pre-placed in this level.
But when I do a little change of this file to show the extra mission, I found it is actually to let the Professor die 10 times.
After I recover that lua file and normal play that level again, I find making the professor die 10 times does not trigger the extra mission, and no Gwen crate shows in the map. I guess maybe there's something wrong with this level.