Bug with word searches (nvm)

I've had problems since I tried making this word search. It consists purely of numbers, and you have to find the strings in question. But for some reason, when I try to submit it, I receive multiple warnings, including that my grid has a density of -0.796 and that there are many blank spaces.

Idk why that happens, but if I'm not wrong, there shouldn't be a problem with alphanumeric characters.

The other time I asked Stewart to help me with it, and although he didn't fix it, he said that my grid became 81x81x81, so I'm the first JetPunker that has made a 3d quiz :D