I think the issue was an async boundary - I was able to trace back to CoreFoundationLibrary but the trail ended there. Also, lldb was unable to get locals? Which is something I’ve not seen happen…

Were you inside the library itself, perhaps?

Yes. That’s where the crash happened. (obviously not the cause, but…)

Yeah, if you are crashing inside the library, you won't have access to locals in that stack frame. You'll need to unwind a bit to your own code until they become visible.