This is more of a general question and not so much about the C8 except the change in behavior has been detected after moving to it.
I have several multi sensors that combine contact, temperature, axis and battery. They are all the same brand and all running the exact same firmware. For those that want to know, they are the original SmartThings multi sensors, but the issue is not limited exclusively to them
Under the previous hub all these devices would periodically wake up and send a battery report, or change in temperature. Under the C8 a few of these sensors continue to check in whereas others don't report at all unless the contact sensor opens/close. Even if the temperature changes dramatically the sensor never wakes up to report it.
Why do seemingly the exact same brand of sensors behave differently from each other, and why on the C8 and not previous hub generations?
It may be possible to change the reporting configuration of ZigBee devices due to a driver provided by @kkossev . Please search for ZigBee reporting in HPM.
There are no options that I see that will change reporting on these devices.
As an experiment I shut down the C8 hub and powered on the C5 that was migrated. To my surprise most of the devices showed up upon boot. I left it running for about 30 minutes and the devices in question all were periodically reporting their status as they should. So it does appear these devices are doing what they're supposed to do but for some reason the C8 isn't processing the reports.
I've also noticed this oddity between the two hubs;
I had problems with z2m (zigbee2mqtt) causing ridiculous battery drain on my devices and I worked with it's author in trying to figure out why. Since I hadn't seen battery issues when the same devices were paired with my C5 I captured and analyzed the zigbee communications during device configuration (when you click Configure) with both systems so I can tell you that the reporting frequency for each data point is setup during this process. These values are individually configurable in z2m but not with HE (currently) so there's nothing you can do except wait for the devs to restore the C5 behavior to the C8.
I was in the minority of z2m users that had battery drain problems and we never did figure out what is different in my setup/use that caused problems. And it wasn't just battery drain, I had devices "go missing" for days/weeks at a time only to magically reappear most, but not all, of the time. I really like much about z2m but moved all my zigbee back to HE because stability trumps. YMMV
