Playback Problem: "repeat previous measure" sign

I am having trouble with playback when I use the "repeat the previous measure" sign that looks kind of like "%" and is found under the "Repeats" palette menu. I added this sign to a measure by clicking on it and dragging it into the measure. The piece plays back correctly until it reaches the measure with the "%" sign in it; then, the playback stops as if that measure were empty. Yes, the "enable repeats" button is turned on at the top of the screen. My actual repeat signs and D.C. al Coda are playing back just fine.

Does anyone know if this is a known bug, or if there is something I can do differently to get these measures to play back? If it makes a difference, I have the latest version of MuseScore and I'm working from a Mac.

Thank you!
Jess