Frequency Drive Spped controller for HVAC air handler

Doing some volunteer work I encountered frequency drives, added to HVAC units to control the blower speed. The frequency drive was instlled near the panel, and the motor leads for the blower came down to the drive and back up to the unit on a #10/4 w/gr MC Cable.
The units ran on eday and responded to the control. The next day some temporary wire was removed and the electrical panel re-organized. Soon the Frequency drive was toast. The HVAC installer said: "That is because you must have changed the phase!" The manufacturer's represenative says that if it is connected "A B" and then changed to "B A" it will 'change the phase and blow up the unit'.
This is a single phase installation, a common five ton high effeciency air handler.

Has anyone encountered this before?

Unless there is something you are not telling us the factory rep is just trying to duck a warranty call.

If there is only one feed into the unit A and B are interchangeable.
The phase changes every 8.33333 milliseconds. Every time you turn this off and turn it back on there is a 50:50 chance which way it will be.

I agree with Greg. While VFD's, PLC's, and other electronic equipment can be a little funny acting at times, I don't see anyway what they are suggesting can be a true possibility for the problem.