You should have the "chunkify" checkbox on by default (or at least warning before people hit one of the Map/Reduce buttons).
People are likely getting their browser tab (perhaps their whole browser) frozen when they click those buttons and having to bail out on your page/submission.
Also, add some overview text instead of a blank page with a ball on it like:
People are likely getting their browser tab (perhaps their whole browser) frozen when they click those buttons and having to bail out on your page/submission.
Also, add some overview text instead of a blank page with a ball on it like:
https://github.com/yangmillstheory/chunkify