Partial OLED static glitch

THANK YOU! That seems to make sense, I did some quick tests and found that commenting out some of the print strings reduced the size of the static. Also, replacing

display.println("Cross test");

with

display.print("Cross");
display.print(" ");
display.println("test");

for some reason seemed to save memory.

I'm still a bit confused as to why this is happening though, since everything I changed was in functions weren't being called. Is there any way to stop them from influencing the other functions when they aren't running.

Also, might you be able to recommend a good resource to learn about using C-style strings as you said in arduino? I tried googling it, but I got a jumble of rather opaque results and discussions/tutorials of regular string use.