There seems to be a bug if the API spec contains more than one API's with colon in the API Path, it always return the response of 1st API.
I have put an example in this repo here: https://github.com/soodpr/oapi-codegen-bug

If we run both server and client code in the above example, the expected output from the client main program is that it first calls the /pets:validate and then /pets:generate API but in reality, its always end up calling /pets:validate API twice.

Let me know if you require any further details on this.