That is an annoyingly buggy behaviour. I have seen a similar problem reported some time ago, but we found no solution, see: aperture will often jump to another image while I'm editing
But it was with an earlier Aperture version and an earlier MacOS.
When editing photos in an iPhoto library opened in Aperture,
Is that the only library where it happens?
Do you see the same, when you create a new library and import some test images?
Can you confirm, that editing in iPhoto will make the difference? That is, that a library, that works well in Aperture alone, will have issues, after opening it in Aperture?
We have two libraries:
- my wife's library used primarily with iPhoto (and originally created as an iPhoto library when iPhoto and Aperture libraries were not cross compatible)
- my library used primarily with Aperture (and originally created as an Aperture library when iPhoto and Aperture libraries were not cross compatible).
The only library where the problem occurs is my wife's "iPhoto" library, when editing in Aperture.
I've now done a complete "Rebuild" of the 'iPhoto" library using the utlilty built into iPhoto. This seems (after limited testing) to have cured the problem.