Problems with Tree

Working on a site constructed in HTML. The site at the moment only has four pages, index, bio, gallery and contact. I have bio page selected and have been adding divs to the structure using the orange underline tool below the element I wish to add the new div. As soon as I try and re-arrange items to nest inside the new div Pinegrow deselects the page I am working on and selects the gallery page, this it does continually not allowing me to stay on the page I am working on. This has happened before I only I did not spot what was happening, I have been editing a page and found I am editing the wrong page and assumed I had accidentally selected it.