Timeline: I press STILL button, but music Doesn't stop.

I use the FM 5.5.3. I have a project in the timeline.
When I press the still button, the cursor stops and I see the respective image in the canvas, that’s fine; however the music does not stop, continue playing! Is it a bug? It happened to me since FM 4. Should I consider any settings on Preferences? Is a question of MEMORY or RAM?

If is not clear, I can send a video showing this weird issue. Thank U! Greetings from Lima-Perú.