Audio Bleed from Track 1 when Recording Track 2

Hello everyone. Yesterday was the first time I tried using Audacity. I’ve never used it before. I would like to see if anyone has any suggestions regarding a problem with Audio Bleed from Track 1 when Recording Track 2. I’ve seen many posts here on the topic, but most are many years old with different versions of Audacity and other things. I experimented with some of the suggestions but nothing helped.

I installed Audacity 2.4.1 on a Windows 8.1 computer. I have a new Alesis Multimix USB 4 FX mixer. The mixer is connecting to the computer via USB cable. Guitar is connected to the Line 2 Guitar jack of the mixer. A separate laptop is providing a backing track via a cable from the laptop headphone jack to the mixer External In jack.

I can record the backing track in Audacity on Track 1 no issues, sounds great. Tried Stereo and Mono. Either way, records fine.

The problem presents itself when I try to record the guitar on Track 2, basically an overdub recorded along with the audio from Track 1. Without even playing the guitar at all there is audio from Track 1 bleeding into Track 2. No combination of Host or Recording Device settings allows me to cleanly record guitar on Track 2 with no audio bleed over from Track 1. Major bummer.

Here are some device settings I have available in Preferences - Devices when the mixer is on.

For Interface Host I have the following options available:
MME
Windows DirectSound
Windows WASAPI

When Interface Host is set as MME I have the following Recording Device options available:
Microsoft Sound Mapper - Input
Line (2- USB AUDIO CODEC)
Stereo Mix (IDT High Definition

When Interface Host is set as Windows DirectSound I have the following Recording Device options available:
Primary Sound Capture Driver
Line (2- USB AUDIO CODEC)
Stereo Mix (IDT High Definition

When Interface Host is set as Windows WASAPI I have the following Recording Device options available:
Digital Output (S/PDIF) (IDT High Definition Audio CODEC) (loopback)
Speakers (2- USB AUDIO CODEC) (loopback)
Speakers / Headphones (IDT High Definition Audio CODEC) (loopback)
Stereo Mix (IDT High Definition Audio CODEC)
Line (2- USB AUDIO CODEC)

I have tried what I believe is every possible combination of settings for Interface Host and Recording Device, and not one would simply allow me to hear Track 1 while I record on Track 2, without getting audio bleed from Track 1 spilling onto Track 2. I even unplugged the guitar to have it out of the picture and the problem still happens.

Would anyone have any idea how I can get Audacity and the mixer to work together without audio bleed from Track 1?

Thanks,
Paul