Any Syriac letter typed following an Arabic Tatweel does not connect to or join the Tatweel.
This ONLY occurs at the very beginning of a new line in MS Word.
After that, the Tatweel connects to the letters until the next line is started.
In this attachment:
RED displays that the Syriac letter is not connected to the Tatweel at the beginning of the line.
BLACK displays the Tatweel and Syriac letters connected.