Curious. Not even if you set your cursor on the a and press TAB again? (I sometimes have to do it twice).

This is what I did:

Downloaded https://orgmode.org/org-9.1.9.zip and unzipped to ~/tmp/org-9.1.9

Ran:
emacs -Q

In the scratch-buffer:
  (add-to-list 'load-path "~/tmp/org-9.1.9/lisp")
  (require 'org)

Switched to a new buffer and did
M-x org-mode RET

Now if I enter that table (e.g. by copy-pasting from my earlier email) and align it, the table becomes misaligned for me when I press TAB when cursor is on the link "a".

I think I'm gonna try to reproduce it with org-mode versions between 8.2.10 and 9.1.9, see what happens.
________________________________
Från: Nicolas Goaziou <mail@nicolasgoaziou.fr>
Skickat: den 7 april 2018 09:38
Till: Thomas P
Kopia: emacs-orgmode@gnu.org
Ämne: Re: links cause table misalignment

Hello,

Thomas P <datalogen@hotmail.com> writes:

> With org-mode 9.1.9, my tables sometimes become misaligned when I press TAB and the cursor is in a cell with a link.
>
> In an org-mode buffer, enter:
>
> | aa | aa |
> | [[a][a]] | |
>
> The lower-left cell becomes misaligned when I press TAB and the cursor
> is on the link "a".

FWIW, I cannot reproduce it. The table is correctly aligned.

Regards,

--
Nicolas Goaziou