My first thought would be a faulty controller in which case I would check ebay for the prices of second hand controllers.
Things I would do with the current equipment,
1) replay the flight in the App's flight history, switch on the display of the control-sticks view and watch what the indicated stick movements were.
2) see if you can start the drone's motors with a CSC ..... NOT with any automated button press. If you can start the motors with the CSC, DO NOT give the drone throttle, just test to see whether or not you can hear or see the propellers respond to not full movements of the RH stick. You can stop the motors by holding the throttle fully closed.
I think full travel stick commands would be safe but I can't remember for certain, hence my saying "not full movement"
3) in the app change the stick mode so that aileron control moves to the LH stick and see if, in calibration, the fault remains with the RH stick etc..
If none of the above changes/fixes anything and the controller is not under warranty and you are 'handy' it might be worth opening the controller to see if you can see anything obviously wrong.
I have no idea what DJI etc. would charge for repairs.
If you were to consider DIY repair by replacing components the first thing I would try is to see if it is possible to switch the connections between the LH & RH hand sticks - I don't remember if the cables are long enough to permit that, nor do I remember if the plugs identical - to see whether the problem remains with the physically RH stick i.e. apparently move to the LH stick, if it does move to the LH stick then I'd say it's a fair guess the LH stick sensors have gone.
Where you would get a stick gimbal might be a problem.
If the problem remained with the apparent RH stick then the real problem lies elsewhere and I'd replace the controller.