Hi Erwin,
I had posted about that case since FontCreator 13, same case in version 14
It is a known issue; FontCreator’s internal shaping engine does not support mixed bidi directions, but it will work correctly with the exported fonts.
That’s clear Erwin, also another issue related to this, if you see I have entered Hindi digits, but it’s appear as Arabic digits (overwirtten picture). The normal situation should seems like in picture below, yes it is work fine when export font, but if there’s hope to seeing it works fine in the preview panel.
I am sorry, but I only know Latin script so without detailed explanation I can’t understand the problem.
O.K, I will see later how to arrange a detailed explanation, maybe with a video record or article or live session. 
This to show the difference between Hindi and Arabic Numerals and how system deal with it.
I am sorry, but I can only see if something is wrong if I have these 3:
- a font
- input text
- an explanation of what the preview shows, and what you expect it to be
Here it is the requested thing, hope to solve it.
overwirtten.rar (1.97 MB)
Thank you for sending the files. Here is my result with the font and the input text:
It seems some magic happens on your side.
O.K Erwin, that is fine 
, I gave up 