The Expert view timeline sometimes zooms in if you drag a clip from Finder or the Project Assets panel to the Expert view timeline. The Expert view timeline can also zoom in if you drag the clip handles to trim a clip.
This behavior is most obvious when working with Adobe Premiere Elements on MacBook Pro with retina display.
Adobe has posted the following fix.
http://helpx.adobe.com/premiere-elements/kb/expert-view-timeline-zoom-in.html
