is your joystick USB or game port type?
how old is it?
I was having problem with my ch Stick, I took it apart, and each individual wire connector was sort of loose, I hooked it up and just barely moved a connector to see how it reacted to the wire moving, it instantly lost calibration........after crimping down all wire conncetors to where they were tight and hard to disconnect, I put stick bak together and recalibrated, the response was almost like it was a new stick.....
if you have had it awhile dust, grit, etc......can find its way into the potentiometers ( what controls different axis inside the stick) and cause you all types of problems, also Logitech have been known to go bad prematurely
if it is USB...try to make sure your USB Port/Rot Hub is in the "Always Power On Mode" so it is not going to sleep on you intermitently , this has caused people to lose the calibration during flight