Update, 4/20/18: This issue should be resolved by a back-end release that is currently in progress.
We are currently working to fix a Sensor Management bug where some sensors are assigned to the incorrect sensor group. The pattern appears when an Admin selects the “Match Any Criteria” and supplies a subsequent rule that does not match any active sensors. The result is that devices will join the group based solely on the operating system that was specified and the priority assigned to the group.
The engineering team has identified the bug and are currently working on and validating a fix for this issue.
As a workaround, once an admin is confident that at least one device with the desired value has checked-in, they should reprocess all groups again. We will update this post with the release timing for this fix as soon as that timeline is clear.
Please refer to the following KB article for more information: Cb Defense: Devices moved to Sensor Group if the criteria doesn't match any Active Sensors