You replaced the Latin font ( ltn0.pvf ) but not the CJK font ( kr0.pvf for Korean/Chinese or jp0.pvf for Japanese). Install a full that replaces all four system font files.
: The system auxiliary partition containing additional language packs, emojis, and fallback characters. Common Font Formats on the Vita ps vita firmware font package
The Ultimate Guide to PS Vita Firmware Font Packages: Customizing Your Handheld You replaced the Latin font ( ltn0
: An additional package containing the system fonts required for UI rendering. Step-by-Step Setup Guide 1. Download the Packages ps vita firmware font package