Typing feedback sometimes slows down

Seemingly at random, VoiceOver's typing feedback will slow down. I'm a normal typist, I believe; not super fast, but not slow. Yet, I can sometimes spend ten or more seconds listening to VO trying to read back characters I've typed as it lags further and further behind. This is with character echo on, word echo off. The voice in use does not seem to matter, and this is a rare problem.