Game runs in DebugGame Editor, but Editor crashes on load in Debug Editor

I wanted to try and edit some engine source, so I am trying to run the editor in Debug Editor mode in VS. It crashes when trying to load my project – a ‘stack overflow’ in LinkerLoad SerializePackageFileSummary().

I know I have run in Debug Editor before – but something must have changed or been added which is crashing it now. Anyone know how I might figure out what is doing it? I don’t see anything in the Call Stack to indicate what it is actually trying to load when it dies.