Non spacing diacritics

I have created some diacritic symbols.

I want to be able to place them without affecting the kerning of the letters between which the diacritic symbol is placed.

I followed instructions in “Roll your own Glyph Data” tutorial to create entries for the diacritic symbols

Here is an example

glyph unicode=“E380” name=“pill1” category=“Mark” subCategory=“Nonspacing” script=“latin” production=“uniE380” description=“Diacritic SYMBOL” />

I made sure Glyphs accepted my additions by checking the Glyph Info Table.

The presence of the diacritic symbol is still affecting the relative position of the letters.

What can I do to ensure the position of the letters are not affected?

Where are you testing?

tested both in Gimp and in Affinity Designer

How do you avoid cache problems? Are you aware of this:
https://www.glyphsapp.com/tutorials/eliminating-font-cache-problems

I think I avoid them by exporting the font using a different name (and Family Name) after editing the file.

I tested it and it seems that Affinity Designer does not interpret the kerning properly. MacOS and Indesign work correctly.