Thanks for the testing, but yeah I’m pretty sure it’s a problem with my installation (I’m on Windows 10 Pro, but it works on my laptop which is Windows 10 Home). Even when I install 4.13 fresh on my main machine, the dlls mentioned in my previous post appear to get modified during startup or cook or something (so something somewhere is saying “hey this engine version is for code projects, let’s build stuff”, even though it’s completely clean).
Anyway I was hoping for a programmer to weigh in on that aspect of it, but I think what I’m going to do is back up all my projects (they’re in perforce anyway), blitz everything remotely UE4-related (including launcher) from my machine and install it all fresh. I’m betting that will fix it.