The project is clearly abandoned by upstream as stated by the maintainer in #27 (comment)

This repo has naturally regressed into a state of deprecation as we at Temando have decided not to make use of this plugin. [...]
I'd recommend someone forks the project and publishes a new package as I don't see us putting effort into this plugin going forward.

Nevertheless, it is still featured in blogs, search results and NPM leading people to experience the same bug(s) over and over (including our team).

Please add a note to

1. the project README (in git),
2. the project description (on GitHub)
3. the npm description,
   stating that the project is in fact abandoned and contains known regressions.

In addition, you could reference a few forks, or possibly coordinate taking over the main npm package name.
https://github.com/conqa/serverless-openapi-documentation by @conqa (it seems this fork the most active)
https://github.com/kzhou57/serverless-openapi-documentation by @kzhou57

For a list of several users reporting the same issue: #24, #25, #27, #28, #29, #32, #34 .