We've identified an issue with collection export feature in Postman Native app versions v6.2.1, v6.2.2, and v6.2.3. Exports to Collection v2.0 and Collection v2.1 formats in these app versions have an additional "_postman_id" field included with every request and folder in the collection. This will not affect the collection from being exported or from being imported into other versions of the Postman app. But we are aware that this issue adds significant friction to workflows that include checking in exported collections into version control systems.
We've identified and isolated the issue to a change in a library we use in the Postman app. We're working on fixing this and release the fix in a patch release this week.
Related GitHub issue: https://github.com/postmanlabs/postman-app-support/issues/4952