I agree with what Diesler said. I did have similar situations before.
Right now, I do have a one-of-a-kind 1/8" sucker fig specimen (3 leaves),
struggling very similar to your TOP shoot. It is currently in my GH under my ICU/TLC,
and doing fine.
My other (possiple) suggestion (that I did have succces with):
Top-UP the soil to "just" cover the old-wood /new-growth.
This may promote some new more-robust-roots from that younger junction/node...
Good luck.