Not sure if related with point 3 of children region issues or something different.
Reference file is the first in the following Forum thread: https://en.smath.com/forum/yaf_postsm59588_Pages-disappear-after-errors.aspx
In row 1989 of the attached file a region having id="186" was created containing all the following regions. Everything since that point can't be seen; no error messages nor error regions are displayed, just the first region (an empty picture).