As title says, a deploy via Ant is failing when trying to deploy a path on opportunity. After searching, I found a few posts on the Salesforce forums back from 2017 related to this issue, but nothing with a resolution. I am opening a case with Salesforce concurrently, but wanted to see if anyone has encountered this while deploying a path, and if so, if there's a resolution.
The short answer provided by Salesforce - you have to deploy the path file on its own.
After a lot of unsuccessful troubleshooting with support, the resolution provided by Salesforce was to run two deploys - the first with all components except the path file, then the second with the pathAssistant file being the only metadata component in the deploy, on its own. This successfully deployed the path, but trying to run a single, complete deploy with the path included afterwards resulted in the same error, effectively preventing it from being included in our continuous integration.
We decided to omit it from our version control/CI altogether based on the above.