The best way to confirm this would be try reproducing the issue without custom policies enabled on the given OU:
- Using the Active Roles MMC Console, navigate to the container/OU hosting the object you are trying to create and/or modify
- Enable Advanced Details Pane under View > Advanced Details Pane
- Click on the container from step 1, and in the Advanced Detail Pane, click on the Active Roles Policy tab
- Block all policies, which are NOT built-in policies
- Custom workflows can also play a part in the experienced behavior. Temporarily disable any of these as well as it could be affecting the OU in question
- Try to reproduce the issue
If the issue is not reproducible enable your custom policies/workflows, one at a time to confirm if the issue can be reproduced. Performing this actions will help to isolate the custom policy/workflow causing the error. Once the policy causing the issue is located, correct the policy rule to resolve the error.