The problem is normally cause by the song having the wrong BPM, the smart loop will loop to the BPM shown in the display... but if the track has been analysed and has detected the wrong BPM then the smart loop will not function as it should.
Try and close the BPM detection range in the options to be closer to your tracks BPM to make it more accurate when analysing.
This script is in my mvkeyboard.vkb file (inside mv folder) edited with notepad. Check if you have these instructions, you must have them as they are by default.