Hi,
This sounds like a Hardware problem with your flightstick (== dirt, accumulated at the end of resistance area of a potentiometer, or worn-out taper of the throttle potmeter of the flightstick ).
Try this:
When the AB has kicked in (so at NO full throttle), press the key assigned to 'full throttle' (default: F4).
WITHOUT touching your flightstick.
If that works OK: your flightstick throttle potmeter is the problem.
Calibrating your flightstick won't help, since it's an intermittant problem.
If it's dirt in the potmeter: the only thing that might help, is cleaning the potmeter with a contact-spray.
But then you have to open-up the flightstick assembly.
But if it's a worn-out potmeter, only remedy is to replace that part (or buy a new flightstick).
Of course, my comment is based on you saying you have the same problem with other aircraft, and that re-callibration doesn't help.
Another way of establishing IF it's a dirty, or worn-out, throttle potmeter of your stick:
Load a flight with a default aircraft, like a 737 or 747.
Shut down the engines, open the VC (or 2D panel window) that shows the Throttles animation).
Now move the Throttle lever on your flightstick for idle to full a few times, and see if it visually 'jitters' at any point (especially in the nearly-full range).
If it does, it's certainly a flightstick hardware problem.
Rob