That sounds like you have assigned the hardware axis to a digital control, i.e. button. Check your controller assignments and make sure the hardware throttle axis has actually been assign to a throttle AXIS in the game controller settings. If it just says “Throttle” that is the wrong kind of assignment.
Hello and thank you for your answers.
I followed your advices, but still the same problem. I reinstalled the software and it worked.
I only had to add 2 plugins. Now each time I install a plugin I will check if it causes anomalies on the throttle.