What manufacturer/model? If Zebra then I prefer using a File Sync with a Post-Install script to execute the firmware update applied to a Virtual Group that has the desired filtering options of OEM Version, model, OS version, Battery level, etc. 

Zebra TC75, Do you have the steps to do the file sync and the post install script?

Create a Virtual Group with Filter Criteria to match your desired conditions, create a File Sync to place the .ZIP into the /sdcard/, add a post-install script to execute the .ZIP with install_system_update. 

I also opened up this discussion on the same topic:

https://discussions.soti.net/thread/zebra-android-os-update-options/