If you session disconnects when you put Termius in the background on your Android device, try disabling battery optimization for the app.
Here’s how you can do that with the most recent Android versions.
Navigate to your device settings.
Choose Apps & notifications > Termius.
From the Advanced section, choose Battery > Battery optimization.
Choose All apps from the drop-down list > Termius > Don’t optimize.
If you still experience the issue after following these steps, please, raise a support request.