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To fix this issue, we recommend that you make a manual relationship between the contact created for the Individual Client Entity and the Company Client Entity. When you make this relationship, ensure you enable folder Access and Folder Read/Write access. Repeat this process for all other Client Entities that this contact needs a relationship with.
For instructions on how to manually create a relationship between a contact and a client entity, please refer to https://nimbusportals.atlassian.net/l/c/bbZJo2Tr
Also search for the contact that shows incorrectly in Nimbus (it is the contact agains against the Company Client Entity) and ensure you have disabled Folder Access, Folder Read/Write and Portal Access.
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