This Salesforce error that Gearset is surfacing occurs when there is a duplicated field value detected in the metadata component you're deploying to the target.
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In this example the error happened on a PR (Pull Request) validation within Pipelines.

To resolve this issue, first identify the duplicated field value referenced as "<xxx>" within the error's message - in this example it is Estimated_Resolution_Date__c (as shown on the above screenshot).
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Next step is to edit the XML file of a failing metadata component (in this example it is Problem-Systems component) using VS Code, or a similar XML editor, and remove one of the duplicated fields from the XML.

Note that you cannot edit the XML file directly in Gearset.
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If the issue happens on a PR validation, you can edit the XML file of the failing component directly within the PR in your Version Control System, and then re-try to validate and merge the PR.
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Alternatively, you can edit the XML file of the failing component directly in your feature branch, remove the duplicated field, and proceed with re-creating your PR.