in the beginning, I also thought this must be a problem with my machine, because otherwise a lot of people must run into it.
But today I got the same Issue at my working place, on a different machine (MacBook Air, 8GB) with another apple ID, also Affinity Designer 1.5 and macOsX Sierra.
Looking forward for a solution, as I introduced Affinity Designer as our new UX-/UI Tool at work.
I attached a file with an embedded document, but this happens NOT just with this document, it crashes everytime I double click on an embedded document in an .afdesign-file :(
thanks for y