Hello again Henri,
well, in the meantime it happened once again. Same situation, same result, no stack trace. Same octree message at the end of the log. Unfortunately it doesn't seem reproducible at will.
Should I manage to find a reasonably good way to do so, I'll be sure to give it a whirl with gdb (if I can still remember how to do it -- I know I did at some point with your help before, so chances are I can find it on the forum).
Love,
Lia