I might have missed it, as the lists are rather long, but I did not see upgrade kit icons vanishing off their upgraded items’ icons, which is another very old bug.
https://forums.funcom.com/t/upgrade-kit-icon-not-showing-after-aos-chapter-3/223804
https://forums.funcom.com/t/kit-icon-absent-from-modified-tools-and-weapons/227756