1st Born vs. 2nd Born?

When Grace was just over 2 years old we transitioned her into her big girl bed.  She did great.  She never got out of bed and we had zero issues.  It was over one year after the transition she got out of bed but stayed in her room.  When I found her sitting on the floor she was so upset and started crying for doing something she thought was wrong (and I didn't even reprimand her).

Today Caleb asked to take a nap in the twin bed in his room that we're hoping to transition him to soon.      I told him he could but that he needed to stay in bed.  He was very tired and said he would.  He's actually a pretty compliant kid so I thought he might.  Three minutes later we heard a door close and went upstairs to find Caleb running all over from room to room.  Back to the crib* he went and we'll tackle this problem in the near future.

*In regards to the crib we are just waiting for the day that Caleb climbs out.  He already climbs in himself so we know he can climb out.  We think he actually has a healthy fear of the floor since it far away.