okey i found the issue and the solution
the issue is they added a line of code in SlateUser.ccp that checks if left mouse button is pressed so it hides if it is. you can just command out or delete this line and recompile the engine to fix it.
i really dont like this change its easy to hide it manuallly with a on mouse down overwrite. but even so if someone from epic sees this PLEASE MAKE THIS A TOGGLE/BOOL. in case of loading bars we might want to keep the tooltip when pressed instead.