I'm glad I'm not the only one that's experiencing this. My own family is not on a 64x64 lot but one of the smaller lots in Ravenwood. I've been dealing with an entirely different bug involving some steps into a sunken sitting area and I have to frequently go into build mode to re-place them. And I've noticed ever since the recent base game patch every time I make any kind of change in build mode specifically (removing those stairs, changing the size of a room, lowering/raising a platform) I experience that freezing issue you're having.
