the problem is in my mouse setting but it also due to TC dividers width.usually i set my mouse speed to fast so very small mouse movement moves the pointer 2 or 3 pixels therefore sometimes the pointer step over the tree divider see this
i never faced this problem with the main left/right divider because its width is 3 pixels while tree dividers are 2 pixels only
maybe you should increase tree dividers width to 3px instead of 2px to solve the problem when set the pointer to max speed or maybe i have to buy a height sensitive mouse
