Well I have 100k items +/- to deal with
Then you should avoid to dereference the pointers to not copy the data around.
I created the base vectors via QVector<myTreeNode> vec(vecSize) and I access them all via , so no thread should step over another thread,
It does as your backtrace shows. Since you're using QVector which is implicit shared every write access to the container checks if the container needs to get detached. Maybe try with a non-implicit shared container instead (e.g. a std::vector)
See http://doc.qt.io/qt-5/implicit-sharing.html for details.