Consider the following text:
----begin example----
---
---
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do
---
---
----end example-----

With auto-fill mode on, continuing to type on the "Lorem ipsum"
line results in the following:
----begin example----
---
---
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do
---eiusmod asdf
---
----end example-----

Notice how "eiusmod" does not start on a new line, as would be expected.
Here is a GIF of this behavior in action:
https://www.dropbox.com/s/w9a803t0qotqe6j/org_autofill_bug.gif?dl=0

Tested with emacs -Q, org 9.3 (lisp that ships with emacs 27)