Why has my Apache mod_wsgi application started dying at regular intervals, even though nothing has changed?

I've had a Flask application served using Apache and mod_wsgi that has been running without issue for months. I haven't touched the Apache config since it launched, and I haven't touched the WSGI application in several weeks.

Two days ago, my application started going down regularly, every 1-2 hours. Specifically, it looks like the Apache parent process is dying/being killed silently.

• No errors in the logs.
• No unusual traffic, and indeed sometimes no traffic at all when it dies (I've sat and seen the process die when no requests have come in for some time).
• I've turned on Apache's forensic logging, and there are no uncompleted requests.
• I've tried setting strict timeouts and limits on the child processes (WSGIDaemonProcess <my_app> processes=5 threads=12 restart-interval=600 inactivity-timeout=60 request-timeout=30 maximum-requests=50), and they are being recycled correctly, but the parent process still dies.
• I've tried changing the MaxRequestWorkers, ServerLimit, and ThreadsPerChild. Adding more ThreadsPerChild seems like it might extend the time before it dies, but that might've been a coincidence.
• I've tested to make sure that any errors coming from my application are logged properly, and they are.
• Neither the parent nor the child processes appear to be using high CPU or memory.
• I've tried stress-testing my application, including creating a long-running test endpoint, in an attempt to reproduce the issue, but I've had no success; it still dies "on schedule"

I have no idea what could be causing this, especially since nothing has apparently changed from before, and at this point I don't even know what to try. Any suggestions would be appreciated.