Settings for 25%, 75%, and 100% work just fine. 50% gives a warning (see log below) and tries to set to "medium low". But, the fan doesn't change speed.
One thing I noticed in the log warning message, I noticed the hyphen was missing from "medium low" when setting the level to 50%. However, the hyphen is present when setting the fan speed to "medium-low" (last command sent in the log).