OU Shows a Duplicate Link After Removing Link From Another Policy. (4370604)

OU Shows a Duplicate Link After Removing Link From Another Policy.

After modifying an OU to remove link from one policy it was noticed that as a result another link was added and it looks to be a duplicate link from another policy that was already linked to the OU as seen below from a screenshot taken from both GPOADmin and GPMC:

 

A possible cause is that when editing an OU for removing or adding a link it could be that the scroll wheel from the mouse is accidentally moved and if the mouse pointer was on top of a linked policy in that very precise moment, then it will scroll through the list of policy and you could end up selecting the name of a policy that was already linked without noticing it. The following screenshot shows Domain Controller OU with 3 GPOs linked. The second link was a different GPO, but the mouse pointer was on top of that GPO name and the mouse scroll wheel was accidentally moved and now the FIREWALL GPO was selected without being noticed leaving that same GPO linked twice:

 

To avoid this in an OU in which multiple GPOs are linked you may try the following:

1- Do not use the scroll wheel and instead use the vertical sliding bar which should be located at the right side of that screen to scroll down.
2- Run difference report between live OU and Working copy to detect any possible duplicate link before deploying changes to correct them.