Quinn, Is there a possibility that Apple may help identifying which particular instruction(s) triggered the ITMS-90755 error, or this is out of question and must be debugged by trial-and-error/guesswork only?

Thanks a lot Kevin and Quinn, Greatly appreciate your detailed responses!

Thanks Quinn, Currently the issue doesn't seem to reproduce on latest macOS (15.5), it seems to be specific to 15.4.1. However, even though it seems to be fixed in newer builds, from what I understand, for future-proofing it is generally not recommended to use dlclose() on libraries like libswiftDemangle.dylib even though I had manually dlopen()'ed previously, and keep such libraries loaded until the application exits?