When mark “arabichamzacomb ($0654)” typed on the Base Character “hehgoal-arab ($06C1)” both disappeared.
Typed Base Character with Mark (ۂ).
screenshot attached FYI.
Font file is also attached.
hehgoal-arab.fcp (175 KB)
It is due to normalization of your input. It is automatically changed to hehgoalhamzaabove-arab.urdu and that glyph in this specific font has no outlines.
Thank you for your support; I was able to identify the mistake once you brought it to my attention.