Imported TTF fonts rendering unknown glyphs for common characters

Imported TTF fonts rendering unknown glyph for previously-working characters such as ' or ! or , or ?. In 4.21 the font was working as expected. User states that custom fonts should be forward-compatible or have a migration tool for newer engine versions.

This was reported and tested in 4.23.1 (CL-9631420). This is reproduced in 4.22.3 (CL-7053642), 4.24 (CL-9868118), and Main 4.25 (CL-9868255).

1. Open the UE4 Editor and create a Blank project
2. Import the attached TTF font
3. Create a Widget with a Text Box and use the font. Include characters such as ! or ?
4. In the Level Blueprint add the widget to Viewport
5. Play in Editor

Results: Custom font shows the "unknown glyph" for simple characters such as ' or !

Expected: Custom font to render normally