Motor Problem

Hello.
We are having some unique trouble with our 269 and 393 motors. We are using RobotC 4.X to program.
Students are just using the debugger mode to explore how sensors and motors function. In debugger mode, we are witnessing this:
enter a motor power level of 127 and nothing happens.
enter a motor power level of 30, and the motor will run.
after entering a motor power level of 30, we can change the power level to 127 and see that the motor does change speed, although this 127 isn’t as fast as it should be (based on using these same systems the past few years).
Any thoughts?
This is obviously going to make the construction and programming of any additional projects a bit of a challenge.
Thanks for any help.
Paul