No groups are displayed for some users

No groups are displayed for some users

When viewing a user's group membership, none of the groups show. This issue isn't with every user, but in about 6 so far. I have attached an example that illustrates issue:

Screenshot 1 shows no groups for this user in AD Manager

Screenshot 2 is the actual group membership of this user, using ADUC who belongs to more than 10 security/dist. lists.   

Any assistance would be greatly appreciated. Thanks

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