Getting "Cannot stringify arbitrary non-POJO" in nuxt fetch

Question

I'm trying to add a "fetch" a function to one of my layouts in our nuxt js project. I'm using nuxt's latest version (2.14.0).

I'm receiving this message on console (server side) when the server is rendering the layout:

WARN  Cannot stringify arbitrary non-POJOs i                                                                                                                                                                      

WARN  Cannot stringify POJOs with symbolic keys Symbol(Symbol.toStringTag)

When I'm removing the fetch function from my layout, this message disappear

at the moment my fetch function doesn't do much

export default {
...      
   fetch () {
        console.log('in fetch')
   }
...
}

I was researching what this WARN message is all about, and as far as I understand this error comes from @nuxt/devalue library.

Does anyone have tips on how to investigate what is the source for this WARN message?

Thanks!