Thanks for the feedback! I'm glad you love the castle and hopefully the minor annoyance with guard's ability to unlock the front door feels not so important by the end. :)
Also note that the front door is NOT the intended entry. The only way through that door is to be seen. You have other ways in that you get in unseen. You can also complete this mission without ever visiting the front door. Good luck!
The guards have keys to the front door on them so they don't get stuck on them trying to go outside for help. In that case they would just sit and run against closed door infinitely during testing. So to avoid that funny / bad situation, I had to give many of them keys to those doors. Other doors that require keys are not like that.
Also, look for other ways in besides the front door itself! There are multiple sneaky ways in!
Yes in the TTLG forum linked in description. I will put on here as well