Okay, looked into the Curious Case of the Missing Letters. It must have been a bug in an earlier version of the code, because when I re-ran the script in its current form, the letters showed up as intended. That's encouraging, at least.

I haven't checked to see if this bug affects any other letters, but Wilhelmine was definitely the first set of letters I generated (per cahn's request!), so it's the most likely to have bugs. I will check the others tomorrow, but for now, I have uploaded a fixed file. These are the letters that were previously missing, which you can go back and read:

207ff
216
228
233
253
257
278
282
286
287
292
297
302
307
310
312
318
321
324
326
328
343

And if you've downloaded this file to read on your Kindle or something, you should redownload it.