Incorrect list of auto-completes in script mode

In script mode, I type “(” and am offered the list of auto-completes I have set up. So far so good.
Eutopia - Scrivener 2015-07-01 14.08.10.png
But then I type the next letter, “H”, and the list changes:
Eutopia - Scrivener 2015-07-01 14.08.56.png
This ain’t what I want! A bug? or is auto-complete not designed to work with brackets?