Hi.
Whenever I have to open something that requires using the ingame keypad to enter a numeric code, I find that inputting a random number can open everything everytime. Even if I close them and try to open them again.
That gives me unlimited access to Dr. Fred's lab after I get the key to open the "Sekrit Lab" door.
I believe that it has something to do with the method used to bypass the copy protection nuclear door.
By the way, I am playing Maniac Mansion v2 with ScummVm 0.12.0 on Windows Vista.
This is *not* caused by ScummVM, but rather a well-known problem with the datafiles. Essentially, these data files contain a crack which bypasses the copy protection, but the way it is done leads to the issue you describe.
See also e.g. <https://sourceforge.net/tracker2/index.php?func=detail&aid=770654&group_id=37116&atid=418820>