what is the poll interval value of your Rhoconnect app?
Did you tried it after increasing the poll interval value?
I don't think that this is linked to the poll interval value in the app.
The "timeout" happens when the Server takes more than 30s to process a request.
Starting from a simple app, with an update source adapter methods that simply sleep for 5s for every request, if there're more than 6 item to update from device to backend, it does not works.
I believe that this is linked to the default NGINX timeout of 30s when proxying connections:
We're currently investigating if increasing these makes any changes.