Okay, it's weird but it's still happening. Org-mode 9.1.5 as above. Hmmm, if I kill the buffer and reopen it, its sorts itself
Here's the header settings
#+STARTUP: showall
#+LANGUAGE: en
#+OPTIONS: H:2 num:nil toc:nil \n:nil
#+OPTIONS: TeX:t LaTeX:t skip:nil d:nil todo:t pri:nil tags:not-in-toc
#+INFOJS_OPT: view:nil toc:nil ltoc:t mouse:underline buttons:0 path:
https://orgmode.org/org-info.js#+EXPORT_SELECT_TAGS: export
#+EXPORT_EXCLUDE_TAGS: noexport
actual text C&P from org buffer
| date | task | time | | |
|----------+---------------------------------------+------+---+---|
| 19/07/12 | admin stuff -- slack, trello, backlog | 3 | | |
| 19/07/16 | meeting. followup. | 2.5 | | |
| | | | | |
screen shot