There have been ongoing problems for several years of iPhoto
getting  into  a  mode  in  which it repeatedly jumps to the
"Last import" event, losing  your  position  and  making  it
difficult to work with images in other events.

The solution reported by several people,  which  has  worked
for me, seems nonsensical:

   cd ~/Pictures/iPhoto\ Library/Auto\ Import
   rm -rf *

When this bug appears, there's always a subdirectory in  the
'Auto Import" directory with a nonsensical name.  It's often
empty, or contains (links to) files that also  have  strange
names.   Anyway,  simply  deleting it (even when it's empty)
seems to fix the problem.  I haven't  even  had  to  restart
iPhoto; it immediately stops the unwanted behavior when this
nonsensical subdirectory disappears.