Bulldogs World

I'm posting in the health forum only because I can't believe she is being naughty.  Maybull is 6 years old and has been perfectly housetrained for 5 1/2 of those years.  About 3 months ago, about once a week, she will poop in the house.  Right in front of you.  I am a stay at home biz owner who has nothing but time to take out my darling bullies.  Rocco is 10 and NEVER had an accident that couldn't be linked to a medical issue.  It is very embarrassing!  Yesterday, in front of guests, while we talking in the kitchen, she just squats and does her thing.  I usually yell, WHAT ARE YOU DOING? and put her out.  I never spank or get aggressive with her.  The poop is perfectly formed, no diarrhea or loose stools.  Sometimes she will go first thing in the morning, 15 minutes before we wake up, in our bedroom where we all sleep.  Sometimes down the hallway.  Never the same spot or same time.  I haven't changed foods.  What are your thoughts?