My Fiskar works great and one of my favorite cutting mats for small pieces. But one of my friends got the same one and had to pop it back onto the base and she's very careful using it on a level surface, too.
I looked at mine to see if there was a "locking chip" on the black rotating base but didn't see anything. But my mat is now 4 years old and has done great for the heavy use it goes through.