There seems to be an issue with key recognition. Try the following and verify the discrepancy with recognized keys in the key history.
That test code doesn't replicate the issue, I think it's a prob ...
I considered the "Input" command - but I would need a way to switch it on and off programatically (at the start and end of the hotkey sequenece) rather than relying on a timeout or a keypres ...
I've been trying to test the [url=http://www.autohotkey.com/forum/viewtopic.php?t=6271]buffered send script and it keeps crashing the latest version of AHK. I also see lots of spurious shift keypress ...