Complex Program Freezes and Breaks

Hey everyone,

I've been having a problem with my more complex program. I have a program that is larger than the size limit that I copy and paste into the editor (for now). It runs smoothly for a while, but then hits some lag spikes and crashes to a screen that looks like this: 

Does anyone know what this specific crash is caused by? You have to refresh the browser to get rid of it. I haven't been able to find any documentation on what causes this, and I'm wondering if it's because the program is too large or if that's just a coincidence.

Thank you