GSX doesn't think anything. It reads the standard engines variables from Simconnect, and if at least one is running, it considers engines to be running. So, there only two possible reasons for this:
- The airplane using a custom internal engine simulation has lost sync with the standard engine variables, which is the only thing GSX can read.
- Simconnect broke due to having reached the maximum limit of Simobjects in flight. This might as well be the cause of both the airplane failing to update Simconnect, but also GSX getting wrong data from it.
You can try restarting GSX after landing, sometimes this might fix the problem
