I occasionally see a problem when Maxim connects to the camera at the beginning of the night. The shutter gets messed up resulting in error 17 on any exposure attempts. I've watched it on the bench and it seems to not always complete the shutter rotation it does when the connect happens. This is intermittent and happens perhaps once every 8-10 connects. Disconnecting and reconnecting Maxim from the camera normally solves the problem and then it runs fine all night. No idea if that is what you are seeing but I thought I would mention it.
Thanks for contributing Geoff. Doesn't sound exactly like my problem but similar. Unfortunately illness has prevented me progressing further so I haven't made any breakthroughs yet. I'll keep your comments in mind when I get back to it. Sent from my iPad using Tapatalk