Apps On The Move

 Say I have a scheduled repeating task

* TODO Go outside                                                               :HABIT:
DEADLINE: <2019-02-09 Sat 21:00 +1d>
<2019-02-09 Sat 09:00 +1d>
SCHEDULED: <2019-02-09 Sat 09:00 +1d>
[2019-02-09 Sat 12:38]

Nothing happens when I go to beorg swipe left and mark DONE, the entry looks exactly the same and beorg still puts it under todo 

I'd expect it to do the same as C-c C-t in emacs? If I mark it DONE in emacs, beorg correctly interprets it and removes the entry from today

Non repeating TODO items work fine

Missing functionality or a bug?

I think the issue is that beorg doesn't repeat both dates, i.e. `SCHEDULED` and `DEDALINE`, only the first of them. Emacs marks the item as done, and then TODO again, but advances both dates +1 day; beorg only advances the first date, `DEADLINE` in your case, so it is still scheduled for today.