In tracking down another problem with the latest version of org (more to
follow probably), I thought using org-lint might help.  With the
attached simple example, I get:

     5 high  Missing definition for footnote [1]

from org-lint.

The footnote definition is there as it's inline...

-- 
: Eric S Fraga via Emacs 26.0.50, Org release_9.0.9-796-gbae41a