I converted some texture packs to resource packs using the tool you provided. When i load them in-game, they work correctly. However, if i close minecraft and open it again, the fonts are completely distorted.

If i switch to the default resource pack and restart minecraft, i can select the texture pack i want to use without any trouble.

1. Start minecraft
2. Select resource pack from converted texture pack
3. Play normally.
4. Close minecraft
5. Fonts are distorted.
6. Select default resource pack.
7. Restart minecraft.
8. Fonts are back to normal.
9. Repeat step 2.