Elk M1, C1M1, and HomeKit

I’ve been using the Elk M1 integration with a M1XEP, HA, and HomeKit for many years. The package has been working great, I can alarm and disarm things remotely, I get alerts via. the HA app, etc.

However, we recently got rid of our land line so I wanted to switch over to cellular and purchased a C1M1. For the most part everything still works, with one notable exception – if the panel resets, we get CO and Fire alarms from HomeKit. Everything else is fine (although it takes a while for the wireless sensors to start reporting again, as expected), and nothing else shows an alarm.

Does anyone have any idea what would be different about the C1M1 that would cause this? More importantly, does anyone have any ideas for either a fix or a workaround? I could probably just exclude those from the HomeKit config, but then I lose visibility into them from there.