Thanks Joe, you're right. That update contained a bug which Microsoft corrected in a March 2018 update, 6 weeks later. The bug was super obscure.

David is this the issue I got from Gordon Spear by email? Is he specifically having as runtime error 76? Or can we get some specific detail? Or maybe his system is way behind on Windows 10 updates and hasn't had the March 2018 update applied? I want to work this issue here and not by email.

He's also concerned about image file naming so if you have questions on that, please by all means post a ticket here. You can look at ACP Help > Customizing ACP > Customizing File and Folder names for info on that. If he is using the web/mobile interface to ACP (and not remoting in and using it as the observatory operator) then he can have any file naming he wants specially for him, with others having their own as well.