Freeside Billing - Bi-monthly automatic payment method not working.

We are running Freeside version 4.2 on Debian Linux 8.10 (Jessie). Only automatic security upgrades are enabled, and they run through the unattended-upgrade script. We intentionally do not upgrade any other packages, to prevent any conflicts with Freeside, and to maximize uptime and reliability overall. Sometime between December 1st and December 15th, Freeside stopped automatically charging our customers that are set to any automatic payment method. We've tried rolling back the few Debian packages that were upgraded during that time, and we haven't seen any difference in the automatic payments. The configuration settings for Freeside have been restricted to only two people including myself, and neither one of us has changed anything in there. When we run the freeside-daily script manually for the last billing cycle (Jan 15th), it appears to run normally, and we get no errors indicating that anything is wrong. This output is comparable to the output we got on December 1, when it last ran successfully: Refer to the uploaded doc. (many similar messages - note that "running cust_event XXXX (realtime_auto) for cust_bill XXXX" messages are present here, but absent in the output from January 15th, in spite of the fact that we still have about 100 customers who haven't had their payments made)