The following issue, may be worth your study - the whole topic web page. That may give you some ideas, on what to pursue:
‘Brave browser displaying thin fonts’
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Other font issues, recently:
‘Font randomly changing to 'Times New Roman' on specific site pages - #2 by Chocoholic’
‘Font not working properly on latest V1.39.111 desktop revision - #2 by 289wk’
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