Confirmed with 'emacs -Q -L ./lisp/ -l org' on latest version of Org.
@Ihor, can you help push me in the right direction in terms of where in the codebase this issue might lie, so that I can examine the related section myself, and also bug a related maintainer about this?
Using Org 9.6 with Emacs 29, write a link:
[[123][test]]
Most of the text will then be hidden, with "test" showing as a link, as
expected. However if I remove the last ], the link highlighting
disappears and only "test" is shown like regular text (/i.e./ instead of
"[[123][test]" as would be expected). If I insert a character at the
end or move the text, it is updated and "[[123][test]" shows as
expected.
(This bug does not occur in Org 9.5 for me.)