openapi-diff v2.1.0 uses swagger-parser v2.1.26, which has the following known issue: swagger-api/swagger-parser#2166
A new version of swagger-parser has been released, which fixed this known issue (v2.1.27).
Currently, we can not bump to openapi-diff-core v2.1.0 because the known issue in swagger-parser v2.1.26 is breaking the build in some of our consumer services.
Please release a new version of openapi-diff-core that uses the new swagger-parser v2.1.27.
Thanks!