Hi Jon.
Looks strange you're in dialout group and have to change the permission. I don't have enough knowledge to guess what could occur. No clue.
Related to the udev's folder, I had an issu within Ubuntu 16.10 and I've copied the rules files in /etc/udev/rules.d and then it works, but no idea why. I've don't find explanation about that.
Unfortunatelly I don't have other suggestion for you.