AHK SendInput will fail if there is no small delay between keystrokes

I made a testcase (see attachments).
I start applcation, wait for its window to be active and send various keystrokes (e.g. TAB, SPACE) using AutoHotKey. When I run my script on Windows, the script succeeds.
When I run my script on ReactOS (e.g. r57536), it fails, but if i add some delay before sending another keystroke - it succeeds. This prevents AHK application tests I am working on to work properly on ReactOS.
VMWare Workstation 9.0