It got to be RightBackDriveMotor.rotateTo(200) call because it is the one that has waitForCompletion argument set to true.
I like @Xenon27 idea that it could be something to do with motor overheating, that inhibits V5 builtin motor PID from reaching the target.
Please, first consider trying changing it from using individual motor statements to drivetrain.
https://api.vexcode.cloud/v5/html/annotated.html
If that fails too then you can change waitForCompletion to false and add timeout. In the event V5 PID gets stuck you will wait an extra second or two and then will keep driving.
If you abandon V5 PID and need check for encoder position and step time then reading this conversation will be useful: