A bug related to the license system has been discovered in 12.8.1. All customers using ATK 12.8.x must upgrade to ATK 12.8.2.
You can obtain the updated 12.8.2 packages from the download page.
The bug is related to how ATK checks out licenses from a floating license servers for a device calculation. Normally only 1 master license is needed, but ATK 12.8.1 it checks out 2 master licenses.
The bug is not present in any earlier versions, but note that 12.8.0 has a few other small bugs that are fixed in 12.8.1 and of course also in 12.8.2.
In addition, an update to the Interface Builder plugin (versoin 1.4) is included ATK 12.8.2, but this can also be downloaded separately via the AddOn Manager.
For more information about new features in ATK 12.8, see the original release letter.