Two Kinect v2 — device factory returned null — libusbK installed, OpenCL confirmed working

Hi,
I'm running iPi Recorder 4.7.0.98 on Windows 10 (10.0.19045.0, 64-bit) with two Xbox One Kinect v2 sensors (Model 1520) and cannot get either camera to stream. Both cameras show as Ready on the Home screen, but display "Could not open a device" when I go to the Setup tab.
My hardware:

Two Microsoft Xbox One Kinect v2 (Model 1520)
ASUS X99 Deluxe motherboard
GTX 1080 Ti, Driver 582.28
One Kinect on Intel USB 3.0 controller (front panel)
One Kinect on Renesas UPD720201 PCIe USB 3.0 expansion card
Windows 10 Home 64-bit

What I have already done:

Uninstalled all Microsoft Kinect SDK and Runtime v1.8 entries completely
Enabled Microsoft Kinect 2 (libfreenect2) in iPi Recorder — shows as installed
Used Zadig 2.9 to install libusbK v3.1.0.0 on all relevant interfaces for both cameras:

Xbox NUI Sensor (Interface 0) — both cameras
Xbox NUI Sensor (Interface 2) — both cameras
Composite Parent entries left on USBCCGP as recommended

Verified with GPU Caps Viewer that OpenCL is fully working: OpenCL 3.0 CUDA 13.0.97 FULL_PROFILE on GTX 1080 Ti
Tried all Depth Processor options: Default, CPU, OpenGL, CUDA — same result on all
Confirmed libusbK is enumerating both devices correctly in the log
Restarted Windows, unplugged all non-essential USB devices

The log shows both cameras enumerating correctly:
libusbK is installed.
Libfreenect2VideoSourceEnumerator: Enumerating
Libfreenect2VideoSourceEnumerator: Enumerated (2 devices)
But then immediately fails:
Libfreenect2VideoSource[003968240147]: Initialized
Libfreenect2VideoSource[003968240147]: Starting streaming
Libfreenect2VideoSource[003968240147]: Could not start streaming: device factory returned null
Libfreenect2VideoSource[206553733947]: Could not start streaming: device factory returned null
Both cameras fail on every single attempt, regardless of which USB port, depth processor setting, or combination I try. The cameras are on separate USB controllers to avoid bandwidth conflicts.
What I have ruled out:

USB controller conflict — cameras are on separate dedicated controllers
libusbK installation — confirmed correct on Interface 0 and Interface 2 for both cameras
OpenCL availability — confirmed fully working via GPU Caps Viewer
Bandwidth — only keyboard and mouse connected during testing

The error device factory returned null appears consistently across all depth processor options, suggesting the libfreenect2 device factory itself cannot open a handle to the physical device, despite libusbK correctly enumerating them.

Has anyone encountered this specific error with dual Kinect v2 on iPi Recorder 4.7.0.98? Is there a known fix, registry edit, or DLL replacement that resolves this?
Full log available on request.

I have confirmed that both cameras work and are functional using the Kinect SDK, but have since been uninstalled to avoid software conflicts.

Thank you