If your device thinks you're scrolling with the joystick even when you're not touching it, you may have one of the following issues: un-calibrated joystick, dirty joystick, or a broken joystick. Fortunately, these are all repairable issues.
Calibrating your joystick can be done through the device settings without any disassembly.
If calibrating the joystick doesn't solve the issue, please refer to the linked guide below:
[[New Nintendo 2DS XL Troubleshooting#Section__The_device_is_not_turning_on|Joystick Repair Guide]]