Guided_NoGPS GCS failsafe issues

I am using the 4.4.4 Arducopter firmware on a 7" drone. The RPI5-based computer sets the Guided_NoGPS mode and then sends the set attitude target. I need a failsafe if the computer program stops for some reason (a voltage or connection problem, for example). I tried to set GUID_TIMEOUT to 0.3. But if I simulate the program crash, the drone continues to fly with the latest attitude I sent. It does not react on RC. It looks like nothing happens after a timeout. I need to return the manual control in this case. Pity that drone fallen from 100m (due to disarm - it was only that worked from RC). Miracle - it has not broken (just a little). But I need now that failsafe urgently.

Mode change using flight mode channel or mode switches should have worked.

Thanks! I will test it, looks like the solution.
Anyway, I don’t understand why it does not exit the Guided No Gps after the timeout.

Just reporting the final working safe&good solution:

On the RC, one stick switches between GNGP and ALTHOLD. The autopilot sets the attitude only if the current mode is GNGP; otherwise, it does not influence the flight. Obviously, if autopilot dies, the drone is still under control.

In the final, I developed an autopilot that optically holds position even on 1000m.