The flip side of inheritance blocking, Enforced GPOs, can cause GPO settings to apply that you were not expecting. When a GPO is marked as Enforced, the settings inside that GPO will blow past inheritance blocking and will apply anyway. If ever there is a situation where inheritance blocking and GPO enforcement are in conflict, Enforce wins!

You can view enforcement settings either by right-clicking on any GPO or a link to that GPO, and look to see whether Enforced is checked. Alternatively, you can click on the OU that you are investigating and take a look at the Linked Group Policy Objects tab. Here you will find a quick summary of all GPOs that are linked to this OU, and can see whether each of them is enforced: