Run script through launch agent is failed
My recommendations:


Move anything to neutral ground:

This removes the launch agent from the launchd database:

sudo launchctl unload /Library/LaunchAgents/com.myapp.plist
sudo launchctl remove com.myapp


Move the .scpt file:

sudo mv ~/Desktop/common.scpt /usr/local/bin/


Remove unneeded std* files:

rm ~/Desktop/stdout.log
rm ~/Desktop/stderr.log


Modify /Library/LaunchAgents/com.myapp.plist with sudo nano /Library/LaunchAgents/com.myapp.plist accordingly:

&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"&gt;
&lt;plist version="1.0"&gt;
&lt;dict&gt;
    &lt;key&gt;Disabled&lt;/key&gt;
    &lt;false/&gt;
    &lt;key&gt;Label&lt;/key&gt;
    &lt;string&gt;com.myapp&lt;/string&gt;
    &lt;key&gt;ProgramArguments&lt;/key&gt;
    &lt;array&gt;
        &lt;string&gt;/usr/bin/osascript&lt;/string&gt;
        &lt;string&gt;/usr/local/bin/common.scpt&lt;/string&gt;
    &lt;/array&gt;
    &lt;key&gt;RunAtLoad&lt;/key&gt;
    &lt;true/&gt;
    &lt;key&gt;StandardErrorPath&lt;/key&gt;
    &lt;string&gt;/tmp/com.myapp.stderr&lt;/string&gt;
    &lt;key&gt;StandardOutPath&lt;/key&gt;
    &lt;string&gt;/tmp/com.myapp.stdout&lt;/string&gt;
    &lt;key&gt;StartInterval&lt;/key&gt;
    &lt;integer&gt;300&lt;/integer&gt;
&lt;/dict&gt;
&lt;/plist&gt;

Increase application kill check delay in the script:

 ...
 repeat until application screenSharingApp is not running
     delay 0.5
 end repeat
 ...

Load the plist:

sudo launchctl load /Library/LaunchAgents/com.myapp.plist





Check that no older "Screen Sharing" app is present on another volume and linked in the launch services database!