Getting started: Worked on understanding the functionality of summary_page.py. The problem with the code is that it was written in one 8000 line python script, with sparse documentation. This makes it difficult to understand and tedious to edit, because it's hard to tell what the precise order of execution is without tracing through the code line by line. In other words, it's difficult to get an overview of what the code generally does, without literally reading all of it. I commented several functions / added docstrings to improve clarity and start fixing this problem.
Crontab: I believe I may have discovered the cause of the 6PM stop on data processing. I am told that the script that runs the summary_pages.py is called every 6 hours. I believe that at midnight, the script is processing the next day's data (which is essentially empty) and thus not updating the data from 6PM to midnight for any of the days.
Git: Finally, created git repository called public_html/__max_40m-summary_testing to use for testing the functionality of my changes to the code (without risking crashing the summary_pages).