I am sorry I can not come up with reproducible steps. It seems random but I have been hit by this issue from every version between 16.0.3061 macOS version and inclusively 16.0.3068 macOS version.
I don’t recall that I have seen this issue on version 15, but at that time I didn’t use FC very often.
The font description of BabelStone Han Basic consists of multiline texts:
“BabelStone Han” is a family of two Unicode CJK fonts in Song/Ming style (宋体/明體) with G-source glyphs used in the People’s Republic of China (PRC). These fonts are derived from the “AR PL Mingti2L Big5” and “AR PL SungtiL GB” fonts (released under the Arphic Public License), converted to Unicode mappings, and expanded to cover all of the main CJK Unified Ideographs block (URO), and a large number of characters in the CJK Unified Ideographs Extensions A through J blocks, including both traditional and simplified character forms.
“BabelStone Han Basic” covers all characters in the CJK Unified Ideographs, CJK Unified Ideographs Extension A, CJK Compatibility Ideographs, and CJK Compatibility Ideographs Supplement blocks, as well as a wide range of other characters in the Basic Multilingual Plane (BMP) and the Supplementary Multilingual Plane (SMP).
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After a few glyph edits/adds and manually modifying “Font Properties Instances → Unique Font Identifier” to reflect the current modification date, there are chances that the “Font Description” becomes truncated into the first line of the text from “‘BabelStone Han’” to “simplified character forms” without any user interaction. That is, the text after “‘BabelStone Han Basic’ covers all characters…” is removed from the font description.
My current workaround is to manually restore the text whenever it gets truncated.