Table bottom border won't always show up

I call this issue: the case of the disappearing border. I have a table that
is surrounded by continuous section breaks (to leave this section unprotected
so users can add additional rows to input information when needed) and for
some reason the bottom border only selectively shows up. Certain things I do
(protect the document, type words into the cells, move the sentence below the
table further down) make the bottom border show up and then later repeating
these steps makes it go away. Other times, I can get the border to show up
for a second and then it will disappear. Something must be interfering with
it, I just don't know what. I have a few "band aid" type tricks that will
mask the problem and make it look normal, but I don't want to send out a form
to users that may have deeper problems that interfere with functionality. Any
ideas on how I can correct this issue?