Are all problematic devices iOS12 devices? Are iOS11 and earlier devices still under control?
Problems occur across all platforms. I have seen 11.2.2 up to 12.1.3 not check in and end up requiring a factory reset. Even a check-in command will not be processed. As you can see in the screen shot below. January 27, last check-in is at 9:26 pm. Device still hadn't checked in next day which required a factory reset. I would like to prevent this and see if there is a way to enable the device to check in. I have tried force restarting the device with Power & Volume down. This will very rarely rectify the problem. Any possible solutions would be greatly appreciated.
As such varied spectrum of your devices are affected, your inputs have steered me towards a totally different direction. Maybe you can try enlarging the request message buffer size with following steps and see if there is any improvement:
1. Open Registry Editor on your MobiControl server, navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\HTTP\Parameters
2. Create a new registry, right click on Parameters and select NEW - > DWORD
3. Set "Name" to MaxRequestBytes and "Value" to 00020000
4. Reboot the MC server