When adding custom fonts (the default8.png file) that is larger than 128x128 pixels, the game will load it correctly, but then after about 3-10 seconds the game will put large amounts of spacing between letters. (See the attached screenshots).
It should load fine and have no spaces, but somehow it puts large spaces between the letters. This has been reproduced all on my iPad, Samsung Galaxy S6, and Windows 10 PC. The screenshots were on Windows 10.
If you would like to reproduce this:
1. Make a new texture pack.
2. Add a default8.png file larger than 128x128 pixels (I used 256x256 in the screenshots) and put it in the fonts folder.
3. Load the game and watch what happens.
I'm trying to port Faithful 32x and this keeps happening to me.
Also, some useful information: This bug never seemed to happen in the first 0.16.0 beta, when the resource pack formats were different.