Play head keeps stopping

Hi I had this problem some time ago and I thought I resolved it ..

But hey presto!!!

It is back again....

There is a button next to the flex tool In Logic Pro x

Which you click if you want the play head to move along wing the song and not disappear off the page at the end of its travel...

The problem is that ..yes it does move with the song when clicked but after the next page the button goes off and I have to keep on pressing it...

Anyone know how to keep this function on?...