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Summary:
When using the "keystroke" function of System Events using AppleScript or from Objective-C with the ScriptingBridge framework, lowercase letters followed after an uppercase letter or symbol that requires the press of the shift key modifier appear as uppercase or mixed case.

This happens even though no modifier keys are pressed on the keyboard while executing the script. In fact no keys are pressed on the hardware keyboard at all.

Also, the actual output is different each time.

I've attached a sample script that illustrates the problem and a short video recording of my screen when the issue happens.

Steps to Reproduce:
1. Open Script Editor
2. Either open the attached sample script or paste this:
tell application "Terminal"
	activate
	tell application "System Events" to keystroke "This is a test"
end tell
3. Watch the output in Terminal.app


Expected Results:
The script should properly print each entered character in the correct casing.

Actual Results:
The casing is different from what was entered and differs with each run.

Version:
macOS Sierra 10.12.2 Beta (16C41b)

Notes:


Configuration:
Approximately every 10 runs the output is actually correct.

Attachments:
'Keystroke Test.scpt' and 'SystemEvents_Keystroke_Bug.mp4' were successfully uploaded.