Sassy back on lock up....

Sassy has had repeated accidents since we returned from Florida.  While not everyday, she manages to not hit the litter box several times a week - always solids.  When she was using the litter box mat I wasn't too concerned, but she's moved to the carpet again.  We brought up the gate and she's back in lock up in the laundry room again.  The first night she's using the litter box again.  I wish we could figure out just what's off with her.  It's all in her head, we've eliminated everything else.  She's such a silly girl.