This is an issue which comes up during the setup process or installation process of converting your machines to a CloudReady machine. You may notice this issue on your my.neverware.com account in the "Devices" section or on your Google Admin Console where the device details are listed. Below, you will find the two common reasons as to why this issue may occur:
1) During a mass deployment process, no matter which deployment tool is used, the image has to be captured before you boot the device. If you boot the device before capturing the image it will write it's MAC ID to the file and saves it as a licensing ID. This leads to capturing the image with the MAC and thereby deploying images with a pre-set MAC ID.
2) If you are connecting to a network via a USB dongle or any other USB ethernet adaptor while the USB installation process is underway, the device again writes its MAC ID as that adaptor's MAC ID. Following this, every other machine that is installed using this same USB installer will have a preset MAC ID of the first device.