Hi curtmc!
Thanks for posting your experience with the game here. The bug you found is a known issue, and I usually see it happen most often during the introduction scenes of the game, but it's sadly possible during the ending cutscenes too.
Included in with the game download is a Help & FAQs text file, and in it I explain the issue you stumbled upon in more detail, but the gist of it is, it's an elusive bug that seems to happen with the RPG Maker MV engine itself, and as far as I am aware, there's really no way to fix it on my end.
It can happen when players are pressing or holding down buttons when the game takes over control of moving the character (during cutscenes or etc.) Doing this speeds up the text and events on screen, and sometimes RPG Maker seems to skip some movement instructions in its haste. Then the game gets stuck and you just have to close it manually as you observed.
Basically, the only real "solution" I've found is the same conclusion you came to, just try not to press or hold unnecessary buttons during parts of the game with scripted movement, and the scenes should play out normally without issues.
For those reading who wish to avoid spoilers, kindly ignore the remainder of this comment.
Let's tackle your other questions:
Pages 5 and 12 as you've no doubt surmised are optional, but I can understand wanting to experience them all (5's encounter is especially fun if I do say so myself.)
You are correct that there is a princess doll involved with Page 5 (good instincts!) and to find it, you'll want to search carefully on the shore. There's a somewhat hidden stretch of beach that you may have missed.
Page 12's encounter is indeed in the part of the mansion beyond that. It's a bit of a tricky one, but it has a nice reward that makes it easier to progress in the mansion without having to backtrack to recover. Probably not much use for you at this point since you've already finished, but perhaps as a convenience for a future play through, or just for completion's sake.
As for Bennie's location after you first get acquainted, she likes to spend time on the beach, getting nice fresh air and some time away from folks for awhile. Search the shoreline areas again and you'll find her.
Hopefully that helps! Thanks again for reaching out, and I'm glad you had an enjoyable experience with the game overall! If you need any further clarification on the hints, just ask.