How would Lightrun have helped here? Skimming their docs, it looks like a fancy debugger that can log stuff on prod and display it in your IDE.

A debugger is most useful when you know where the problem is and you can either reproduce it or it occurs often enough to observe. Neither was true for OP. Additionally, the problem was in nginx and it's not clear if the error was visible from a part of the stack that Lightrun supports.

That said, I'm always game to hear about alternative debugging techniques.