Hi Alfio,
The way that is built is likely that happen. Are you using the last version with the SDK?
The SDK wrapper version helps us to isolate that instance in another request because a service action is used to wrap up the extension actions. It should not have the same instance for different requests.
To try to solve it you can try to make your own action server wrapper to wrap this up or you can download the last version, where you can see how that was improved.
Let me know if that worked.
Sorry for taking too much to reply I'm really excited to see it working in a real scenario, so anything that you would like to discuss please, reach me out.
Cheers,
Paulo