I am not sure what is going on here. I have this minor mode defined,
as shown yesterday, where I just iterate through a buffer and try to
make certain lines invisible.

It seems that visibility property updates only for about 2 ~ 3 pages of
text. When I bring text into visible portion of screen and re-run the
mode, it is updated as it should. Does it have to do something with how
invisible text is rendered? I think it shouldn't but I don't understand
what is going on here? The search seems to properly find all src markers
in entire buffer, and all lines are "equal" (machine generated), so
there is no reason why some parts should work and others dont.

Another issue is with minor mode definition. I am trying to use
mode-variable to toggle on/off as I understand the docs it should be
used, but I have to call it twice in org file. Do I need to use
another boolean value to check on, or could I use mode-variable for this
purpose? I thought it was ment for this.