Char that displayed fine stops working after a minute of game running. requires rebuild to fix

I’m in Unity 2021.3.1f1
using font NotoSansSC font to display Chinese characters. The font displays fine when I first create the TMP_Font Asset. After a minute or so of the game running in the editor, some characters that displayed fine before stop displaying

I get the following warning:
The character with Unicode value \u5B66 was not found in the [NotoSansSC-Regular SDF 2] font asset or any potential fallbacks. It was replaced by Unicode character \u25A1 in text object [Text (TMP)].
after about a minute of the game running in the editor

if I delete ‘Library’ or recreate the TMP_Font Asset using right click Create>TextMeshPro>Font Asset, it starts working again

any idea what would cause this issue? Thank you!

ok its a dynamic population mode issue. I changed Generation Settings in the font asset. Set atlas width/height to 4k and checked “multiple atlas” solved the issue. Sorry, new to text mesh pro :slight_smile: