Dang, I really thought I fixed it, apparently there was a second bug like it.
Did you restart from beginning or tried with the old save? Maybe it's corrupted (normally it wouldn't change anything, I'm asking just in case).
Other possibility is just that the calculation for the brick placement is too heavy: my computer can freeze 1 second when too much brick is placed at once (but at higher zoom level, not currently in game). How would you rate your computer ? Low-end, middle, high-end?