I've found an alternative
var pos_a = event.global_pos - get_global_transform_with_canvas().get_origin() node.set_global_pos(pos_a) #pos_a *camera_zoom
For this node.set_global_pos(get_global_mouse_pos()) has been confirmed as a bug, hopefully quickly closed
https://github.com/godotengine/godot/issues/7990