Another thing for the Apple III emulation that I have encountered a bit lately is the fonts don't get loaded well / get corrupted when testing with my problock3 driver. On the real machine i don't have any issue.

I had a bit of look at the schematic trying to understand how they load. It looks like one of the enables for the font loading is when the screen is in the VBL period, in the Apple II/III this is 1/4 of the total screen scan time (I love that book Understanding the Apple II by Jim Sather). I think what really should happen is the char rams get loaded progressively as the vbl scan period scans the screens holes following the same quirky Apple II/III memory scheme. I hope that makes some sense.

The current trigger for font loading is when VBL starts, it then loads them all. I did a quick mod to invert the call to load the fonts (added .invert()) so it does the character load at the end of the VBL period, and it works much better. I did get a font error once with BOS, but much better visually with this quick fix.