While my checkouts continue to update I looked over the changes made by [1d6747e53fa1fc82].

My current primary suspect is the call to "TclNRYieldObjCmd" at the end of "TclNRYieldToObjCmd", going from "clientData" to "INT2PTR(CORO_ACTIVATE_YIELDM))".

... Update complete, I can now build and actually start trialing.