After updating to OS X 10.10.2, you may find that VoiceOver will not announce all characters when entering text.
Typically, there are 3-4 characters which VoiceOver does not announce after they have been typed.
There appears to be no pattern as to which letters will be effected.
This behaviour has been encountered with various TTS voices.
Bug First Encountered
How often the bug occurs
Simply switching to another TTS voice may remove this behaviour. Alternatively, deleting and redownloading the effected TTS voice via the VoiceOver Utility has also been known to resolve the problem.
Deleting and redownloading the TTS voice had fixed this problem for me. However, it’s come back again after a few weeks, but now with a different set of letters not being announced (i, d and l). It’s only for lower case right now. For what it’s worth, I’m using the Ava voice.
All quite frustrating, really.