In a previous project I needed to create separate USDZ files for each animation - one animation per USDZ file. I loaded the first USDZ model and kept both the model and animation. For additional animations I loaded the USDZ file, kept the animation, and dumped the model part. I could then apply the animations to the full model I loaded first.

I figured out one way to do it from Apple's source code. I posted the solution here: https://developer.apple.com/forums/thread/724014

Figured it out! I needed to plug-in my phone and build for the actual device (as opposed to the simulator) Building for Any iOS Device (arm64) works too.

Looks like the optimal lensPosition changes over time. Could temperature change from device usage and ambient temperature changes affect the optimal lensPosition? If so, it looks like I will have to recalibrate lensPosition on a regular basis.

Success! In another thread someone mentioned installing older versions of Autodesk software, and that did the trick for me too. (Note: This is still with Monterey 12.2 not the 12.3 beta where I initially had problems) Here is the previous thread where I found the suggestion to try older versions of Autodesk software. https://developer.apple.com/forums/thread/661927

Follow-up 2: The app was approved, and I tested the In-App Purchase. It worked as expected! :-) So it appears all the extra passwords required (3 altogether for the first purchase) for Sandboxed user and TestFlight testing is just an artifact of the testing process.

Follow-up: I get the same behavior (enter Apple ID + password, followed by entering password twice more) for first IAP in both TestFlight and when using a sandbox account. A second IAP purchase works as expected (enter your password just once). I took Apple's StoreKit 2 demo app, changed the Bundle ID, created an app on App Store Connect with all the same IAP items in the demo, and purchased items through a sandboxed account. I get the same behavior from Apple's demo code: enter Apple ID + password, followed by entering password twice more. I went ahead and submitted the app for review. I hope the non-TestFlight and non-Sandboxed behavior (i.e., a real user purchase) is better. Fingers crossed!