Explanation of the error
This Salesforce error that Gearset is surfacing is usually encountered when only selected parts of a Custom object are being deployed (partial deployment), and a required tag is not present in the deployment.
Most likely, this is caused when a new part of a Custom object is created, but we are deploying through a Delta CI job, and therefore the entire Custom object is either not present or the tag is not being surfaced to Gearset from Salesforce.
Resolution
To work around this issue, run a comparison via Compare and deploy in Gearset to commit the entire Custom object metadata into the target branch.
Or you can deploy your new Custom object directly both to the environment branch (source of CI) and the Salesforce org (usually a target of your CI job).
To be edited later: Quick note that someone will need to add a cause here. This can also be caused by managed packages not being included in the metadata filter.
Further examples of this Salesforce validation error can be found here:
Disclaimer: This error is returned by Salesforce directly, rather than Gearset. Even so, we offer guidance based on our combined experience with the Metadata API. Where possible, we try to help guide you to fix or avoid this error. In the case that this isn't possible, we may need to direct you to Salesforce support for further clarification.