Alternate glyphs for kerning pairs in serif version do not get bolded

[bookzombie]

I've noticed alternate glyphs for kerning pairs do not get bolded correctly in the serif version.
For example, it should be "first" (bold on "fir") but will display as "first" (bold only on "r" while "fi" is ignored).
Same with "flight" (should bold the "flig") but it will instead display "flight" (bolding the "ig" but ignoring the "fl").
These are just a couple I've noticed so far, it is possible other alternate glyphs are being overlooked as well.
Thanks

[Born2Root]

Hi,
thank you for the detailed report.
Still I am not able to replicate the behaviour.

Please see the following screenshot as a reference.
Bolding works exactly like it should.

Now the question is why it is not working on your system.
With which reader or software are you using the font?

[bookzombie]

Hi,
I am using a Kindle Paperwhite 11th generation (2021), firmware version 5.18.2.