Crackling noise when patching MCV-10 AUX CV to Behringer 2-XM (VCA/VCF)

The Setup:

• MIDI-to-CV Interface: MCV-10
• Synthesizer: Behringer 2-XM
• Routing: I configured the AUX out of the MCV-10 to send Breath Control (CC #2). I am patching this into the VCA CV and VCF CV inputs on the 2-XM.

The Issue:

Whenever I play my MIDI controller, I get a noticeable crackling noise coming through the speakers. If I physically disconnect the MCV-10 from the 2-XM entirely, the noise disappears, leading me to strongly suspect the MCV-10's AUX CV connection is the culprit.

Troubleshooting Steps I've Already Taken:

• Voltage check: Before patching, I measured the AUX output voltage on the MCV-10. It reads between 0V and +10V, which is exactly what I expected.
• Ground loop isolation: I suspected a USB ground loop, so I completely disconnected the USB connections for both the 2-XM and the MCV-10 from my PC.
• Power isolation: I ran the MCV-10 off a portable battery pack to completely isolate its power. Unfortunately, the exact same crackling noise is still present.

My Question:

Has anyone experienced a similar issue with this gear combination, or does anyone have suggestions on how to filter, isolate, or troubleshoot this CV crackling noise? Any advice would be greatly appreciated!