Hi Laura S,
Thank you for reaching out to us on Microsoft Q&A Forum.
Please try the below troubleshoot steps
Check the configuration of your sequences in Dynamics 365 to ensure they are set up correctly. Verify if there are any duplicate triggers or conditions that could be causing sequences to fire multiple times.
Review the segments that you have deactivated due to issues with leads hitting the default assignment. Determine if these segments can be reactivated after resolving the underlying assignment rule problems.
After making any adjustments to sequence settings or work assignment rules. Validate that sequences are firing correctly and that leads are being assigned to the appropriate sales agents without duplication.
Check the work assignment rules in Dynamics 365. Ensure that they are configured correctly and that there are no conflicts or overlaps in the rules that could lead to unexpected behavior.
If you are still facing any issue, please let us know in the comments. We are glad to help you.
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