The function eZContentObjectTreeNode::assignSectionToSubTree does not clear the global $eZContentObjectContentObjectCache variable. This can be very tricky.

Suppose you assign another section of the published object's main node subtree in a pre-publish workflow event. Then the publish operation will still store the object again with it's old section id, because the object will come out of the cache in eZContentOperationCollection::setObjectStatusPublished.