After installing Server 2012 R2 Core and fully patching with Windows Updates I tried to install the GUI and it failed. I found countless search results in Google with the same issue. This happens whether you install the GUI and try to change to Core or install Core and try to change to GUI. It works until you patch for the first time.
The fix seems to be to manually apply every update that is installed on your server to the install.wim file. Otherwise your server files are different than the source that the install-windowsfeature / uninstall-windowsfeature is looking at. Has anyone found an easy work around for this? There are a number of scripts I found in the search results but I am curious if Microsoft ever addressed this problem.
This might be a helpful real world tip to offer in the training video.