So, my issue was never about live_call() line placement, rather than about something failing to load functions from other extensions. I was able to reproduce the issue in an empty project with only extensions being GMLive and Quality Structures, so maybe latter is the culprit here. Edit: tried it with other extension (file_ini) and same error happens.
if (live_call()) return live_result; ini = file_ini_open("test.ini"); /// results in [live][2020-09-28 10:27:23] Runtime error: [error] `instance#100002(Test)` (Test) does not have a variable `file_ini_open` called from Test:Step_0[L3,c7]
Here's that test project: <snip>
Is there any way I could fix it on my own? Please, I'm addicted to live development now.