Not here. Created a stereo file in SF with 20 sec 1kHz 20 seconds 100% L followed by 20 sec 100% R. Master Bus output meters, soundcard output, WAV saved from CD-A, and burned CD all correctly follow the test signal.
Split (unlock) the Master output level controls - L changes L meter and audio out, and likewise R changes R.
Identical results using a mono source file.
You don't have some panning plugin installed on the event, or on the Master FX chain by default ? Or are you sure that you're not standing on your head ;-)