Multitrack session reverts to original imported audio file when I edit

Hi there,

I'm editing a podcast and my multitrack view and session keeps taking me back into the original imported audio file when I go to move or edit a clip in the multitrack view ie. I am completely out of the multitrack timeline every time I try to nudge, move, edit. It is making editing almost impossible. Has anyone else had this? Have I accidentally checked a preference I don't want?

Thanks for your help.