I'm using several libraries (Pods) in source form - which I would expect to show up in the debugger if they were misbehaving - and one binary framework. The framework is a custom Metal-based mapping engine and while it does create layers they are always children of the host UIView and shouldn't have any impact on the layout. I won't say it's impossible, but I've been using the same framework for 2+ years without any problems.If this is my code or something from a 3rd party library, why doesn't the call stack show it? I would at least expect to see some kind of "enqueued from" indicator that I could use to track down the source of the offending call.

My code is, definitely, the first suspect in this. But I've been running the app in the debugger with the main thread checker engaged for days and while I've caught other issues I've never managed to trap this particular issue.As I said, it doesn't appear to be taking place in my code, so I can't tell what view is the source. What you see in the trace is what I get. I can't find any point in my code where I'm manipulating constraints that might be called from a background thread or queue. As you can see, this error takes place on a thread that's executing system code - there's no reference in there to my app ("FlightBox_PFD").Any suggestions?