Another puzzling challenge

After the 1000 piece "son -in- law's revenge" jigsaw, my Mother decided she would try a 500 piece puzzle, but this is proving tricky too. 
She was too tired this evening, after a hospital appointment, to do anymore of it, so I took a look and discovered a few pieces in the wrong  places, which wasn't helping with its completion! I think we'll soon have it wrapped now.