Issues with panning on song

Im using version 2.2.2 running windows 10.
I have no issues recording normally.
Im recording an old track from dat through my mixer.
When recording both left and right channels levels are fine but there is a particular part of the track where there is a synth sound that pans from left to right quite quickly back and forth.
Its like its not recording equally on both sides, although both left and right channels are the right level, instead of panning the sound fades in and out and jumps up and down in volume.
Obviously the track plays fine straight out of the mixer not going through the computer.
Thanks for any help you might offer.

Check your cables/connections: are you recording stereo, rather than mono ?. (If it’s mono there will be no panning).
Are all Windows audio enhancements switched off ?, (in both the recording & the playback tabs of Windows sound).

Like Trebor, my guess is that you are only recording one audio channel. That will occur if the recording device is set to mono in the Windows Sound settings (see:
Ensure that the recording device is set to “2 channels (stereo)”.