DR-40 xlr stereo recording yields only one clear channel

[mathmason]

I am recording via a shotgun Mic Audio Technica AT875r. When I record in Stereo EXT IN 1/2, it shows only one channel recording. When I do record, the left channel is always heavily muffled compared to the right channel. Phantom power is on. How do I get it to record clear stereo to both channels? The strange thing is when I do switch the xlr cable from the left Neutrik input to the right one, the clear recording changes to the left and the right channel becomes muffled.

Can someone explain to me how I can get clear and proper stereo recording despite this?

Many Thanks