LoadFromCacheOrDownload and PlayerPref.SetFloat (WebGL)

I'm using PlayerPrefs.GetFloat and PlayerPrefs.SetFloat to save the player's personal volume preferences.

This works great, until I create a coroutine that contains a basic, nearly copied from the manual LoadFromCacheOrDownload.

Loading the game to test, after the bundle loads (automatic and immediately before switching scenes) and upon initially trying to save (using PlayerPrefs.SetFloat("randomString",0.5f), I get the error "Invoking error handler due to TypeError: invalid arguments".

It seems to read the settings just fine. The sliders are set perfectly when I go into the options. It just throws the error on trying to save.

Is this a bug with WebGL? I haven't been able to find anything else about this problem.