The socket drag opperator stores the index of the last picked socket into RNA in case the user mouse cursor leaves the link while dragging.
This can not work since it tries to retrieve the stored link by this id (which is not uniqe) from all links in edittree.
This patch changes the way the last picked link is stored and stores a pointer to the link directly into SpaceNode_Runtime instead.
{F9802243}
Video of the bug by @pablovazquez