It seems that AEM does not like the GET paths with parameters, or any PUT/POST operations, from my original swaggerfile. However it is a tricky process through trial and error to find out what specifically is causing the problem. Trace logger on error.log didn't yield any new info.
This issue is caused when the swagger file is invalid, hence there is no swagger definition has been found. Could you verify the swagger has valid format. YAML can be tricky format sometimes. IF still facing problem, convert it to JSON online and verify schema online. It may make things easier.