load-doc-err.ts

loadDocuments$ = this.actions$.pipe(
   ofType<documentActions.Fetch>(documentActions.FETCH)
   switchMap((action) =>
       this.documentsService
         .getDocuments().pipe(
            map(docs => new documentActions.FetchSuccess(docs)),
            catchError(error => of(
                  new ErrorOccurred({
                      action,
                      error,
                  })
              ))
          )
    )
)

I think you want this:

• action can be taken from the switchMap argument.
• typo in err. You are using error in the new ErrorOccurred

loadDocuments$ = this.actions$.pipe(
   ofType<documentActions.Fetch>(documentActions.FETCH)
   switchMap((action) =>
       this.documentsService
         .getDocuments().pipe(
            map(docs => new documentActions.FetchSuccess(docs))
            catchError(error => of(
                  new ErrorOccurred({
                      action,
                      error,
                  })
              ))
          )
    )
)