Is it possible that Google crawler doesn't fetch all the content on the page when it's size is 1.6 MB? How does Google treat big documents?
There are in general no page size limits established by Google. Only Google News pages should be not bigger then 256 kB.
But the size of the page makes some limitations by design, which could prevent proper crawling. Such limitations, where the crawler just gets off, are i.e.:
- exorbitant nesting of the DOM tree
- too much links in above-the-fold area
- load time too slow (i.e. because of too many assets included in the head)
- assets, which Google means they were important, aren't crawlable (blocked by robots, unavailable by server)
- too many 404 errors coming from page's assets (images etc.)
- content, loaded dynamically AND which visibility is triggered by user's action
The page's size doesn't matter. What matters, is whether the crawler has any obstacle in its way.