Default enable/disable setting for old posts keeps resetting to disallow

Because of the nature of my site content, I want comments to be enabled for all posts indefinitely. To that end, I’ve UNCHECKED the option under Settings -> Discussion -> Automatically close comments on articles older than 28 days. This works, and my posts allow comments just fine.

BUT, every so often (it can be a few weeks, or a few days), this option will check itself again, and comments are disabled. I have no idea why it’s happening. I go in and uncheck it, and it’s fine again until the next time it decides to reset. I’ve even tried changing the default “28 days” to “10000 days” in the hopes that the re-checking won’t matter, but it resets the days to 28 as well!

Any idea what’s happening and why? The random occurrences would make sense if it is tied to automatic WordPress updates, but I don’t get any sort of notification when updates occur, so I can’t correlate. But if that is the case, it’s a bug that needs to be fixed. Updates should not be altering existing settings.