Going full static giving issue on few pages with forms

I have a nuxtJS application, I am following this documentation to implement Jamstack: https://nuxtjs.org/blog/going-full-static/

I am able to generate the deployment files successfully. When I try to test the build locally using: nuxt serve. Some of my pages which have forms on them are crashing with following error:

vendors~app.f051bb2.js:2 TypeError: Cannot read property 'defaultClient' of undefined
    at Re (app.c94d6ea.js:1)
    at app.c94d6ea.js:1
    at h (app.fd2bc81.js:2)
    at Generator._invoke (app.fd2bc81.js:2)
    at Generator.next (app.fd2bc81.js:2)
    at r (app.fd2bc81.js:2)
    at l (app.fd2bc81.js:2)

Any clues please? We are using APIs in our application, which are working successfully on some pages.