Question S-Voice starts with feedback muted?

Since updating my i747 to 4.3 OTA, when starting up S-Voice the voice feedback prompts (the app reading the results back to me) are always muted, requiring me to push the button on the lower-left to turn the voice responses on. This only fixes things temporarily, since the next time the app starts from scratch the feedback is muted again. It seems like it should be the other way around by default. This isn't related to my phone's volume control, either. The update to 4.3 works well otherwise, as I did a factory reset after installing. Can someone else with the same config tell me whether or not this is happening to them? I want to know if this is a software bug or if I might need to restore the firmware in the future.

EDIT: I found the cause! It's Greenify's accessibility service.