NO Control of right side motor in teleop, but works fine in autonomous mode

Has anyone encountered an issue that you cannot control a motor (right motor with right joystick) in teleop with joystick controller, but the motor obeys commands fine in autonomous mode?? It failed when conducting driver trials yesterday. Have checked all hardware, wiring and ports. All firmware is up to date, including RobotC. Even tried 2nd controller, issue still persists. Can anyone help???

Since it’s custom code, it would help to see it to debug it, post it here. I’ve run into it a few times, and it’s always been setting motor value at the top of the loop and setting it to zero at the bottom.

How to debug, take two roboteers, one becomes LEFT motor, one is RIGHT motor. Read the code out loud, have them act. You’ll soon see where it fails.