Inconsistent Token Refresh Behavior

Question

When I attempt to refresh a Podio access token by making a request to the refresh token endpoint within a Next.js API route, the token returned is often the old, stale token instead of a new one. However, when I perform the same operation in an identical, local script, the token refreshes correctly every time. Does anyone know if the refresh token endpoint distinguishes between calls made from server-side?

var myHeaders = new Headers();
      myHeaders.append("Content-Type", "application/json");
      myHeaders.append("Cache-Control", "no-store, max-age=0");

      var raw = JSON.stringify({
        grant_type: "refresh_token",
        client_id: podio_app_id,
        client_secret: client_key,
        refresh_token: refresh_token,
      });

      var requestOptions = {
        method: "POST",
        headers: myHeaders,
        body: raw,
      };
      const response = await fetch(
        "https://api.podio.com/oauth/token/v2",
        requestOptions
      );
      if (!response.ok) {
        console.log(response);
        throw new Error(`HTTP error! status: ${response.status}`);
      }

      const data = await response.json();
      console.log(data); // returns stale token in server. returns new token locally

I set a refresh_by time. If the current time exceeds refresh_by time, then a refresh is attempted server side. The token returned to the server is often stale, and the same token is returned repeatedly. The expected behavior is a new access token being returned with each call to the refresh endpoint.